1 files changed, 0 insertions, 97 deletions
diff --git a/spec/ruby/core/array/shared/join.rb b/spec/ruby/core/array/shared/join.rb
index 507b13e3c8..93d5329ee3 100644
--- a/spec/ruby/core/array/shared/join.rb
+++ b/spec/ruby/core/array/shared/join.rb
@@ -1,103 +1,6 @@
 require_relative '../fixtures/classes'
 require_relative '../fixtures/encoded_strings'
 
-describe :array_join_with_default_separator, shared: true do
-  before :each do
-    @separator = $,
-  end
-
-  after :each do
-    $, = @separator
-  end
-
-  it "returns an empty string if the Array is empty" do
-    [].send(@method).should == ''
-  end
-
-  it "returns a US-ASCII string for an empty Array" do
-    [].send(@method).encoding.should == Encoding::US_ASCII
-  end
-
-  it "returns a string formed by concatenating each String element separated by $," do
-    suppress_warning {
-      $, = " | "
-      ["1", "2", "3"].send(@method).should == "1 | 2 | 3"
-    }
-  end
-
-  it "attempts coercion via #to_str first" do
-    obj = mock('foo')
-    obj.should_receive(:to_str).any_number_of_times.and_return("foo")
-    [obj].send(@method).should == "foo"
-  end
-
-  it "attempts coercion via #to_ary second" do
-    obj = mock('foo')
-    obj.should_receive(:to_str).any_number_of_times.and_return(nil)
-    obj.should_receive(:to_ary).any_number_of_times.and_return(["foo"])
-    [obj].send(@method).should == "foo"
-  end
-
-  it "attempts coercion via #to_s third" do
-    obj = mock('foo')
-    obj.should_receive(:to_str).any_number_of_times.and_return(nil)
-    obj.should_receive(:to_ary).any_number_of_times.and_return(nil)
-    obj.should_receive(:to_s).any_number_of_times.and_return("foo")
-    [obj].send(@method).should == "foo"
-  end
-
-  it "raises a NoMethodError if an element does not respond to #to_str, #to_ary, or #to_s" do
-    obj = mock('o')
-    class << obj; undef :to_s; end
-    -> { [1, obj].send(@method) }.should raise_error(NoMethodError)
-  end
-
-  it "raises an ArgumentError when the Array is recursive" do
-    -> { ArraySpecs.recursive_array.send(@method) }.should raise_error(ArgumentError)
-    -> { ArraySpecs.head_recursive_array.send(@method) }.should raise_error(ArgumentError)
-    -> { ArraySpecs.empty_recursive_array.send(@method) }.should raise_error(ArgumentError)
-  end
-
-  it "uses the first encoding when other strings are compatible" do
-    ary1 = ArraySpecs.array_with_7bit_utf8_and_usascii_strings
-    ary2 = ArraySpecs.array_with_usascii_and_7bit_utf8_strings
-    ary3 = ArraySpecs.array_with_utf8_and_7bit_binary_strings
-    ary4 = ArraySpecs.array_with_usascii_and_7bit_binary_strings
-
-    ary1.send(@method).encoding.should == Encoding::UTF_8
-    ary2.send(@method).encoding.should == Encoding::US_ASCII
-    ary3.send(@method).encoding.should == Encoding::UTF_8
-    ary4.send(@method).encoding.should == Encoding::US_ASCII
-  end
-
-  it "uses the widest common encoding when other strings are incompatible" do
-    ary1 = ArraySpecs.array_with_utf8_and_usascii_strings
-    ary2 = ArraySpecs.array_with_usascii_and_utf8_strings
-
-    ary1.send(@method).encoding.should == Encoding::UTF_8
-    ary2.send(@method).encoding.should == Encoding::UTF_8
-  end
-
-  it "fails for arrays with incompatibly-encoded strings" do
-    ary_utf8_bad_binary = ArraySpecs.array_with_utf8_and_binary_strings
-
-    -> { ary_utf8_bad_binary.send(@method) }.should raise_error(EncodingError)
-  end
-
-  context "when $, is not nil" do
-    before do
-      suppress_warning do
-        $, = '*'
-      end
-    end
-
-    it "warns" do
-      -> { [].join }.should complain(/warning: \$, is set to non-nil value/)
-      -> { [].join(nil) }.should complain(/warning: \$, is set to non-nil value/)
-    end
-  end
-end
-
 describe :array_join_with_string_separator, shared: true do
   it "returns a string formed by concatenating each element.to_str separated by separator" do
     obj = mock('foo')
diff --git a/spec/ruby/core/array/all_spec.rb b/spec/ruby/core/array/all_spec.rb
new file mode 100644
index 0000000000..680e8c26fa
--- /dev/null
+++ b/spec/ruby/core/array/all_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#all?" do
+  @value_to_return = -> _ { true }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :all?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].all?(/bar/) { false }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/allocate_spec.rb b/spec/ruby/core/array/allocate_spec.rb
new file mode 100644
index 0000000000..c9eceef590
--- /dev/null
+++ b/spec/ruby/core/array/allocate_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+describe "Array.allocate" do
+  it "returns an instance of Array" do
+    ary = Array.allocate
+    ary.should.instance_of?(Array)
+  end
+
+  it "returns a fully-formed instance of Array" do
+    ary = Array.allocate
+    ary.size.should == 0
+    ary << 1
+    ary.should == [1]
+  end
+
+  it "does not accept any arguments" do
+    -> { Array.allocate(1) }.should.raise(ArgumentError)
+  end
+end
diff --git a/spec/ruby/core/array/any_spec.rb b/spec/ruby/core/array/any_spec.rb
new file mode 100644
index 0000000000..b51ce62f0f
--- /dev/null
+++ b/spec/ruby/core/array/any_spec.rb
@@ -0,0 +1,49 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#any?" do
+  describe 'with no block given (a default block of { |x| x } is implicit)' do
+    it "is false if the array is empty" do
+      empty_array = []
+      empty_array.should_not.any?
+    end
+
+    it "is false if the array is not empty, but all the members of the array are falsy" do
+      falsy_array = [false, nil, false]
+      falsy_array.should_not.any?
+    end
+
+    it "is true if the array has any truthy members" do
+      not_empty_array = ['anything', nil]
+      not_empty_array.should.any?
+    end
+  end
+
+  describe 'with a block given' do
+    @value_to_return = -> _ { false }
+    it_behaves_like :array_iterable_and_tolerating_size_increasing, :any?
+
+    it 'is false if the array is empty' do
+      empty_array = []
+      empty_array.any? {|v| 1 == 1 }.should == false
+    end
+
+    it 'is true if the block returns true for any member of the array' do
+      array_with_members = [false, false, true, false]
+      array_with_members.any? {|v| v == true }.should == true
+    end
+
+    it 'is false if the block returns false for all members of the array' do
+      array_with_members = [false, false, true, false]
+      array_with_members.any? {|v| v == 42 }.should == false
+    end
+  end
+
+  describe 'when given a pattern argument' do
+    it "ignores the block if there is an argument" do
+      -> {
+        ['bar', 'foobar'].any?(/bar/) { false }.should == true
+      }.should complain(/given block not used/)
+    end
+  end
+end
diff --git a/spec/ruby/core/array/append_spec.rb b/spec/ruby/core/array/append_spec.rb
new file mode 100644
index 0000000000..5480d9f65e
--- /dev/null
+++ b/spec/ruby/core/array/append_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#<<" do
+  it "pushes the object onto the end of the array" do
+    ([ 1, 2 ] << "c" << "d" << [ 3, 4 ]).should == [1, 2, "c", "d", [3, 4]]
+  end
+
+  it "returns self to allow chaining" do
+    a = []
+    b = a
+    (a << 1).should.equal?(b)
+    (a << 2 << 3).should.equal?(b)
+  end
+
+  it "correctly resizes the Array" do
+    a = []
+    a.size.should == 0
+    a << :foo
+    a.size.should == 1
+    a << :bar << :baz
+    a.size.should == 3
+
+    a = [1, 2, 3]
+    a.shift
+    a.shift
+    a.shift
+    a << :foo
+    a.should == [:foo]
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array << 5 }.should.raise(FrozenError)
+  end
+end
+
+describe "Array#append" do
+  it "is an alias of Array#push" do
+    Array.instance_method(:append).should == Array.instance_method(:push)
+  end
+end
diff --git a/spec/ruby/core/array/array_spec.rb b/spec/ruby/core/array/array_spec.rb
new file mode 100644
index 0000000000..855f17348f
--- /dev/null
+++ b/spec/ruby/core/array/array_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+
+describe "Array" do
+  it "includes Enumerable" do
+    Array.include?(Enumerable).should == true
+  end
+end
diff --git a/spec/ruby/core/array/assoc_spec.rb b/spec/ruby/core/array/assoc_spec.rb
new file mode 100644
index 0000000000..a5026cf5d4
--- /dev/null
+++ b/spec/ruby/core/array/assoc_spec.rb
@@ -0,0 +1,52 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#assoc" do
+  it "returns the first array whose 1st item is == obj or nil" do
+    s1 = ["colors", "red", "blue", "green"]
+    s2 = [:letters, "a", "b", "c"]
+    s3 = [4]
+    s4 = ["colors", "cyan", "yellow", "magenta"]
+    s5 = [:letters, "a", "i", "u"]
+    s_nil = [nil, nil]
+    a = [s1, s2, s3, s4, s5, s_nil]
+    a.assoc(s1.first).should.equal?(s1)
+    a.assoc(s2.first).should.equal?(s2)
+    a.assoc(s3.first).should.equal?(s3)
+    a.assoc(s4.first).should.equal?(s1)
+    a.assoc(s5.first).should.equal?(s2)
+    a.assoc(s_nil.first).should.equal?(s_nil)
+    a.assoc(4).should.equal?(s3)
+    a.assoc("key not in array").should == nil
+  end
+
+  it "calls == on first element of each array" do
+    key1 = 'it'
+    key2 = mock('key2')
+    items = [['not it', 1], [ArraySpecs::AssocKey.new, 2], ['na', 3]]
+
+    items.assoc(key1).should.equal?(items[1])
+    items.assoc(key2).should == nil
+  end
+
+  it "ignores any non-Array elements" do
+    [1, 2, 3].assoc(2).should == nil
+    s1 = [4]
+    s2 = [5, 4, 3]
+    a = ["foo", [], s1, s2, nil, []]
+    a.assoc(s1.first).should.equal?(s1)
+    a.assoc(s2.first).should.equal?(s2)
+  end
+
+  it "calls to_ary on non-array elements" do
+    s1 = [1, 2]
+    s2 = ArraySpecs::ArrayConvertible.new(2, 3)
+    a = [s1, s2]
+
+    s1.should_not_receive(:to_ary)
+    a.assoc(s1.first).should.equal?(s1)
+
+    a.assoc(2).should == [2, 3]
+    s2.called.should.equal?(:to_ary)
+  end
+end
diff --git a/spec/ruby/core/array/at_spec.rb b/spec/ruby/core/array/at_spec.rb
new file mode 100644
index 0000000000..3c7c99fdff
--- /dev/null
+++ b/spec/ruby/core/array/at_spec.rb
@@ -0,0 +1,56 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#at" do
+  it "returns the (n+1)'th element for the passed index n" do
+    a = [1, 2, 3, 4, 5, 6]
+    a.at(0).should == 1
+    a.at(1).should == 2
+    a.at(5).should == 6
+  end
+
+  it "returns nil if the given index is greater than or equal to the array's length" do
+    a = [1, 2, 3, 4, 5, 6]
+    a.at(6).should == nil
+    a.at(7).should == nil
+  end
+
+  it "returns the (-n)'th element from the last, for the given negative index n" do
+    a = [1, 2, 3, 4, 5, 6]
+    a.at(-1).should == 6
+    a.at(-2).should == 5
+    a.at(-6).should == 1
+  end
+
+  it "returns nil if the given index is less than -len, where len is length of the array"  do
+    a = [1, 2, 3, 4, 5, 6]
+    a.at(-7).should == nil
+    a.at(-8).should == nil
+  end
+
+  it "does not extend the array unless the given index is out of range" do
+    a = [1, 2, 3, 4, 5, 6]
+    a.length.should == 6
+    a.at(100)
+    a.length.should == 6
+    a.at(-100)
+    a.length.should == 6
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    a = ["a", "b", "c"]
+    a.at(0.5).should == "a"
+
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(2)
+    a.at(obj).should == "c"
+  end
+
+  it "raises a TypeError when the passed argument can't be coerced to Integer" do
+    -> { [].at("cat") }.should.raise(TypeError)
+  end
+
+  it "raises an ArgumentError when 2 or more arguments are passed" do
+    -> { [:a, :b].at(0,1) }.should.raise(ArgumentError)
+  end
+end
diff --git a/spec/ruby/core/array/bsearch_index_spec.rb b/spec/ruby/core/array/bsearch_index_spec.rb
new file mode 100644
index 0000000000..e1d5eb66bb
--- /dev/null
+++ b/spec/ruby/core/array/bsearch_index_spec.rb
@@ -0,0 +1,81 @@
+require_relative '../../spec_helper'
+require_relative '../enumerable/shared/enumeratorized'
+
+describe "Array#bsearch_index" do
+  context "when not passed a block" do
+    before :each do
+      @enum = [1, 2, 42, 100, 666].bsearch_index
+    end
+
+    it "returns an Enumerator" do
+      @enum.should.instance_of?(Enumerator)
+    end
+
+    it "returns an Enumerator with unknown size" do
+      @enum.size.should == nil
+    end
+
+    it "returns index of element when block condition is satisfied" do
+      @enum.each { |x| x >= 33 }.should == 2
+    end
+  end
+
+  it "raises a TypeError when block returns a String" do
+    -> { [1, 2, 3].bsearch_index { "not ok" } }.should.raise(TypeError)
+  end
+
+  it "returns nil when block is empty" do
+    [1, 2, 3].bsearch_index {}.should == nil
+  end
+
+  context "minimum mode" do
+    before :each do
+      @array = [0, 4, 7, 10, 12]
+    end
+
+    it "returns index of first element which satisfies the block" do
+      @array.bsearch_index { |x| x >= 4 }.should == 1
+      @array.bsearch_index { |x| x >= 6 }.should == 2
+      @array.bsearch_index { |x| x >= -1 }.should == 0
+    end
+
+    it "returns nil when block condition is never satisfied" do
+      @array.bsearch_index { false }.should == nil
+      @array.bsearch_index { |x| x >= 100 }.should == nil
+    end
+  end
+
+  context "find any mode" do
+    before :each do
+      @array = [0, 4, 7, 10, 12]
+    end
+
+    it "returns the index of any matched elements where element is between 4 <= x < 8" do
+      [1, 2].should.include?(@array.bsearch_index { |x| 1 - x / 4 })
+    end
+
+    it "returns the index of any matched elements where element is between 8 <= x < 10" do
+      @array.bsearch_index { |x| 4 - x / 2 }.should == nil
+    end
+
+    it "returns nil when block never returns 0" do
+      @array.bsearch_index { |x| 1 }.should == nil
+      @array.bsearch_index { |x| -1 }.should == nil
+    end
+
+    context "magnitude does not effect the result" do
+      it "returns the index of any matched elements where element is between 4n <= xn < 8n" do
+        [1, 2].should.include?(@array.bsearch_index { |x| (1 - x / 4) * (2**100) })
+      end
+
+      it "returns nil when block never returns 0" do
+        @array.bsearch_index { |x| 1 * (2**100) }.should == nil
+        @array.bsearch_index { |x| (-1) * (2**100) }.should == nil
+      end
+
+      it "handles values from Integer#coerce" do
+        [1, 2].should.include?(@array.bsearch_index { |x| (2**100).coerce((1 - x / 4) * (2**100)).first })
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/array/bsearch_spec.rb b/spec/ruby/core/array/bsearch_spec.rb
new file mode 100644
index 0000000000..12aec60654
--- /dev/null
+++ b/spec/ruby/core/array/bsearch_spec.rb
@@ -0,0 +1,84 @@
+require_relative '../../spec_helper'
+require_relative '../enumerable/shared/enumeratorized'
+
+describe "Array#bsearch" do
+  it "returns an Enumerator when not passed a block" do
+    [1].bsearch.should.instance_of?(Enumerator)
+  end
+
+  it_behaves_like :enumeratorized_with_unknown_size, :bsearch, [1,2,3]
+
+  it "raises a TypeError if the block returns an Object" do
+    -> { [1].bsearch { Object.new } }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if the block returns a String" do
+    -> { [1].bsearch { "1" } }.should.raise(TypeError)
+  end
+
+  context "with a block returning true or false" do
+    it "returns nil if the block returns false for every element" do
+      [0, 1, 2, 3].bsearch { |x| x > 3 }.should == nil
+    end
+
+    it "returns nil if the block returns nil for every element" do
+      [0, 1, 2, 3].bsearch { |x| nil }.should == nil
+    end
+
+    it "returns element at zero if the block returns true for every element" do
+      [0, 1, 2, 3].bsearch { |x| x < 4 }.should == 0
+
+    end
+
+    it "returns the element at the smallest index for which block returns true" do
+      [0, 1, 3, 4].bsearch { |x| x >= 2 }.should == 3
+      [0, 1, 3, 4].bsearch { |x| x >= 1 }.should == 1
+    end
+  end
+
+  context "with a block returning negative, zero, positive numbers" do
+    it "returns nil if the block returns less than zero for every element" do
+      [0, 1, 2, 3].bsearch { |x| x <=> 5 }.should == nil
+    end
+
+    it "returns nil if the block returns greater than zero for every element" do
+      [0, 1, 2, 3].bsearch { |x| x <=> -1 }.should == nil
+
+    end
+
+    it "returns nil if the block never returns zero" do
+      [0, 1, 3, 4].bsearch { |x| x <=> 2 }.should == nil
+    end
+
+    it "accepts (+/-)Float::INFINITY from the block" do
+      [0, 1, 3, 4].bsearch { |x| Float::INFINITY }.should == nil
+      [0, 1, 3, 4].bsearch { |x| -Float::INFINITY }.should == nil
+    end
+
+    it "returns an element at an index for which block returns 0.0" do
+      result = [0, 1, 2, 3, 4].bsearch { |x| x < 2 ? 1.0 : x > 2 ? -1.0 : 0.0 }
+      result.should == 2
+    end
+
+    it "returns an element at an index for which block returns 0" do
+      result = [0, 1, 2, 3, 4].bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
+      [1, 2].should.include?(result)
+    end
+  end
+
+  context "with a block that calls break" do
+    it "returns nil if break is called without a value" do
+      ['a', 'b', 'c'].bsearch { |v| break }.should == nil
+    end
+
+    it "returns nil if break is called with a nil value" do
+      ['a', 'b', 'c'].bsearch { |v| break nil }.should == nil
+    end
+
+    it "returns object if break is called with an object" do
+      ['a', 'b', 'c'].bsearch { |v| break 1234 }.should == 1234
+      ['a', 'b', 'c'].bsearch { |v| break 'hi' }.should == 'hi'
+      ['a', 'b', 'c'].bsearch { |v| break [42] }.should == [42]
+    end
+  end
+end
diff --git a/spec/ruby/core/array/clear_spec.rb b/spec/ruby/core/array/clear_spec.rb
new file mode 100644
index 0000000000..15778f864f
--- /dev/null
+++ b/spec/ruby/core/array/clear_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#clear" do
+  it "removes all elements" do
+    a = [1, 2, 3, 4]
+    a.clear.should.equal?(a)
+    a.should == []
+  end
+
+  it "returns self" do
+    a = [1]
+    a.should.equal? a.clear
+  end
+
+  it "leaves the Array empty" do
+    a = [1]
+    a.clear
+    a.should.empty?
+    a.size.should == 0
+  end
+
+  it "does not accept any arguments" do
+    -> { [1].clear(true) }.should.raise(ArgumentError)
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    a = [1]
+    a.freeze
+    -> { a.clear }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/clone_spec.rb b/spec/ruby/core/array/clone_spec.rb
new file mode 100644
index 0000000000..7ce9d40a81
--- /dev/null
+++ b/spec/ruby/core/array/clone_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/clone'
+
+describe "Array#clone" do
+  it_behaves_like :array_clone, :clone
+
+  it "copies frozen status from the original" do
+    a = [1, 2, 3, 4]
+    b = [1, 2, 3, 4]
+    a.freeze
+    aa = a.clone
+    bb = b.clone
+
+    aa.should.frozen?
+    bb.should_not.frozen?
+  end
+
+  it "copies singleton methods" do
+    a = [1, 2, 3, 4]
+    b = [1, 2, 3, 4]
+    def a.a_singleton_method; end
+    aa = a.clone
+    bb = b.clone
+
+    a.respond_to?(:a_singleton_method).should == true
+    b.respond_to?(:a_singleton_method).should == false
+    aa.respond_to?(:a_singleton_method).should == true
+    bb.respond_to?(:a_singleton_method).should == false
+  end
+end
diff --git a/spec/ruby/core/array/collect_spec.rb b/spec/ruby/core/array/collect_spec.rb
new file mode 100644
index 0000000000..bdee5c240a
--- /dev/null
+++ b/spec/ruby/core/array/collect_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Array#collect" do
+  it "is an alias of Array#map" do
+    Array.instance_method(:collect).should == Array.instance_method(:map)
+  end
+end
+
+describe "Array#collect!" do
+  it "is an alias of Array#map!" do
+    Array.instance_method(:collect!).should == Array.instance_method(:map!)
+  end
+end
diff --git a/spec/ruby/core/array/combination_spec.rb b/spec/ruby/core/array/combination_spec.rb
new file mode 100644
index 0000000000..ac570687ca
--- /dev/null
+++ b/spec/ruby/core/array/combination_spec.rb
@@ -0,0 +1,74 @@
+require_relative '../../spec_helper'
+
+describe "Array#combination" do
+  before :each do
+    @array = [1, 2, 3, 4]
+  end
+
+  it "returns an enumerator when no block is provided" do
+    @array.combination(2).should.instance_of?(Enumerator)
+  end
+
+  it "returns self when a block is given" do
+    @array.combination(2){}.should.equal?(@array)
+  end
+
+  it "yields nothing for out of bounds length and return self" do
+    @array.combination(5).to_a.should == []
+    @array.combination(-1).to_a.should == []
+  end
+
+  it "yields the expected combinations" do
+    @array.combination(3).to_a.sort.should == [[1,2,3],[1,2,4],[1,3,4],[2,3,4]]
+  end
+
+  it "yields nothing if the argument is out of bounds" do
+    @array.combination(-1).to_a.should == []
+    @array.combination(5).to_a.should == []
+  end
+
+  it "yields a copy of self if the argument is the size of the receiver" do
+    r = @array.combination(4).to_a
+    r.should == [@array]
+    r[0].should_not.equal?(@array)
+  end
+
+  it "yields [] when length is 0" do
+    @array.combination(0).to_a.should == [[]] # one combination of length 0
+    [].combination(0).to_a.should == [[]] # one combination of length 0
+  end
+
+  it "yields a partition consisting of only singletons" do
+    @array.combination(1).to_a.sort.should == [[1],[2],[3],[4]]
+  end
+
+  it "generates from a defensive copy, ignoring mutations" do
+    accum = []
+    @array.combination(2) do |x|
+      accum << x
+      @array[0] = 1
+    end
+    accum.should == [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
+  end
+
+  describe "when no block is given" do
+    describe "returned Enumerator" do
+      describe "size" do
+        it "returns 0 when the number of combinations is < 0" do
+          @array.combination(-1).size.should == 0
+          [].combination(-2).size.should == 0
+        end
+        it "returns the binomial coefficient between the array size the number of combinations" do
+          @array.combination(5).size.should == 0
+          @array.combination(4).size.should == 1
+          @array.combination(3).size.should == 4
+          @array.combination(2).size.should == 6
+          @array.combination(1).size.should == 4
+          @array.combination(0).size.should == 1
+          [].combination(0).size.should == 1
+          [].combination(1).size.should == 0
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/array/compact_spec.rb b/spec/ruby/core/array/compact_spec.rb
new file mode 100644
index 0000000000..dbcd16da35
--- /dev/null
+++ b/spec/ruby/core/array/compact_spec.rb
@@ -0,0 +1,51 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#compact" do
+  it "returns a copy of array with all nil elements removed" do
+    a = [1, 2, 4]
+    a.compact.should == [1, 2, 4]
+    a = [1, nil, 2, 4]
+    a.compact.should == [1, 2, 4]
+    a = [1, 2, 4, nil]
+    a.compact.should == [1, 2, 4]
+    a = [nil, 1, 2, 4]
+    a.compact.should == [1, 2, 4]
+  end
+
+  it "does not return self" do
+    a = [1, 2, 3]
+    a.compact.should_not.equal?(a)
+  end
+
+  it "does not return subclass instance for Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3, nil].compact.should.instance_of?(Array)
+  end
+end
+
+describe "Array#compact!" do
+  it "removes all nil elements" do
+    a = ['a', nil, 'b', false, 'c']
+    a.compact!.should.equal?(a)
+    a.should == ["a", "b", false, "c"]
+    a = [nil, 'a', 'b', false, 'c']
+    a.compact!.should.equal?(a)
+    a.should == ["a", "b", false, "c"]
+    a = ['a', 'b', false, 'c', nil]
+    a.compact!.should.equal?(a)
+    a.should == ["a", "b", false, "c"]
+  end
+
+  it "returns self if some nil elements are removed" do
+    a = ['a', nil, 'b', false, 'c']
+    a.compact!.should.equal? a
+  end
+
+  it "returns nil if there are no nil elements to remove" do
+    [1, 2, false, 3].compact!.should == nil
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.compact! }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/comparison_spec.rb b/spec/ruby/core/array/comparison_spec.rb
new file mode 100644
index 0000000000..14e8931e5a
--- /dev/null
+++ b/spec/ruby/core/array/comparison_spec.rb
@@ -0,0 +1,97 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#<=>" do
+  it "calls <=> left to right and return first non-0 result" do
+    [-1, +1, nil, "foobar"].each do |result|
+      lhs = Array.new(3) { mock("#{result}") }
+      rhs = Array.new(3) { mock("#{result}") }
+
+      lhs[0].should_receive(:<=>).with(rhs[0]).and_return(0)
+      lhs[1].should_receive(:<=>).with(rhs[1]).and_return(result)
+      lhs[2].should_not_receive(:<=>)
+
+      (lhs <=> rhs).should == result
+    end
+  end
+
+  it "returns 0 if the arrays are equal" do
+    ([] <=> []).should == 0
+    ([1, 2, 3, 4, 5, 6] <=> [1, 2, 3, 4, 5.0, 6.0]).should == 0
+  end
+
+  it "returns -1 if the array is shorter than the other array" do
+    ([] <=> [1]).should == -1
+    ([1, 1] <=> [1, 1, 1]).should == -1
+  end
+
+  it "returns +1 if the array is longer than the other array" do
+    ([1] <=> []).should == +1
+    ([1, 1, 1] <=> [1, 1]).should == +1
+  end
+
+  it "returns -1 if the arrays have same length and a pair of corresponding elements returns -1 for <=>" do
+    eq_l = mock('an object equal to the other')
+    eq_r = mock('an object equal to the other')
+    eq_l.should_receive(:<=>).with(eq_r).any_number_of_times.and_return(0)
+
+    less = mock('less than the other')
+    greater = mock('greater then the other')
+    less.should_receive(:<=>).with(greater).any_number_of_times.and_return(-1)
+
+    rest = mock('an rest element of the arrays')
+    rest.should_receive(:<=>).with(rest).any_number_of_times.and_return(0)
+    lhs = [eq_l, eq_l, less, rest]
+    rhs = [eq_r, eq_r, greater, rest]
+
+    (lhs <=> rhs).should == -1
+  end
+
+  it "returns +1 if the arrays have same length and a pair of corresponding elements returns +1 for <=>" do
+    eq_l = mock('an object equal to the other')
+    eq_r = mock('an object equal to the other')
+    eq_l.should_receive(:<=>).with(eq_r).any_number_of_times.and_return(0)
+
+    greater = mock('greater then the other')
+    less = mock('less than the other')
+    greater.should_receive(:<=>).with(less).any_number_of_times.and_return(+1)
+
+    rest = mock('an rest element of the arrays')
+    rest.should_receive(:<=>).with(rest).any_number_of_times.and_return(0)
+    lhs = [eq_l, eq_l, greater, rest]
+    rhs = [eq_r, eq_r, less, rest]
+
+    (lhs <=> rhs).should == +1
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    (empty <=> empty).should == 0
+    (empty <=> []).should == 1
+    ([] <=> empty).should == -1
+
+    (ArraySpecs.recursive_array <=> []).should == 1
+    ([] <=> ArraySpecs.recursive_array).should == -1
+
+    (ArraySpecs.recursive_array <=> ArraySpecs.empty_recursive_array).should == nil
+
+    array = ArraySpecs.recursive_array
+    (array <=> array).should == 0
+  end
+
+  it "tries to convert the passed argument to an Array using #to_ary" do
+    obj = mock('to_ary')
+    obj.stub!(:to_ary).and_return([1, 2, 3])
+    ([4, 5] <=> obj).should == ([4, 5] <=> obj.to_ary)
+  end
+
+  it "does not call #to_ary on Array subclasses" do
+    obj = ArraySpecs::ToAryArray[5, 6, 7]
+    obj.should_not_receive(:to_ary)
+    ([5, 6, 7] <=> obj).should == 0
+  end
+
+  it "returns nil when the argument is not array-like" do
+    ([] <=> false).should == nil
+  end
+end
diff --git a/spec/ruby/core/array/concat_spec.rb b/spec/ruby/core/array/concat_spec.rb
new file mode 100644
index 0000000000..1e8d20c36c
--- /dev/null
+++ b/spec/ruby/core/array/concat_spec.rb
@@ -0,0 +1,74 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#concat" do
+  it "returns the array itself" do
+    ary = [1,2,3]
+    ary.concat([4,5,6]).equal?(ary).should == true
+  end
+
+  it "appends the elements in the other array" do
+    ary = [1, 2, 3]
+    ary.concat([9, 10, 11]).should.equal?(ary)
+    ary.should == [1, 2, 3, 9, 10, 11]
+    ary.concat([])
+    ary.should == [1, 2, 3, 9, 10, 11]
+  end
+
+  it "does not loop endlessly when argument is self" do
+    ary = ["x", "y"]
+    ary.concat(ary).should == ["x", "y", "x", "y"]
+  end
+
+  it "tries to convert the passed argument to an Array using #to_ary" do
+    obj = mock('to_ary')
+    obj.should_receive(:to_ary).and_return(["x", "y"])
+    [4, 5, 6].concat(obj).should == [4, 5, 6, "x", "y"]
+  end
+
+  it "does not call #to_ary on Array subclasses" do
+    obj = ArraySpecs::ToAryArray[5, 6, 7]
+    obj.should_not_receive(:to_ary)
+    [].concat(obj).should == [5, 6, 7]
+  end
+
+  it "raises a FrozenError when Array is frozen and modification occurs" do
+    -> { ArraySpecs.frozen_array.concat [1] }.should.raise(FrozenError)
+  end
+
+  # see [ruby-core:23666]
+  it "raises a FrozenError when Array is frozen and no modification occurs" do
+    -> { ArraySpecs.frozen_array.concat([]) }.should.raise(FrozenError)
+  end
+
+  it "appends elements to an Array with enough capacity that has been shifted" do
+    ary = [1, 2, 3, 4, 5]
+    2.times { ary.shift }
+    2.times { ary.pop }
+    ary.concat([5, 6]).should == [3, 5, 6]
+  end
+
+  it "appends elements to an Array without enough capacity that has been shifted" do
+    ary = [1, 2, 3, 4]
+    3.times { ary.shift }
+    ary.concat([5, 6]).should == [4, 5, 6]
+  end
+
+  it "takes multiple arguments" do
+    ary = [1, 2]
+    ary.concat [3, 4]
+    ary.should == [1, 2, 3, 4]
+  end
+
+  it "concatenates the initial value when given arguments contain 2 self" do
+    ary = [1, 2]
+    ary.concat ary, ary
+    ary.should == [1, 2, 1, 2, 1, 2]
+  end
+
+  it "returns self when given no arguments" do
+    ary = [1, 2]
+    ary.concat.should.equal?(ary)
+    ary.should == [1, 2]
+  end
+end
diff --git a/spec/ruby/core/array/constructor_spec.rb b/spec/ruby/core/array/constructor_spec.rb
new file mode 100644
index 0000000000..c4398c535d
--- /dev/null
+++ b/spec/ruby/core/array/constructor_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array.[]" do
+  it "returns a new array populated with the given elements" do
+    obj = Object.new
+    Array.[](5, true, nil, 'a', "Ruby", obj).should == [5, true, nil, "a", "Ruby", obj]
+
+    a = ArraySpecs::MyArray.[](5, true, nil, 'a', "Ruby", obj)
+    a.should.instance_of?(ArraySpecs::MyArray)
+    a.inspect.should == [5, true, nil, "a", "Ruby", obj].inspect
+  end
+end
+
+describe "Array[]" do
+  it "is a synonym for .[]" do
+    obj = Object.new
+    Array[5, true, nil, 'a', "Ruby", obj].should == Array.[](5, true, nil, "a", "Ruby", obj)
+
+    a = ArraySpecs::MyArray[5, true, nil, 'a', "Ruby", obj]
+    a.should.instance_of?(ArraySpecs::MyArray)
+    a.inspect.should == [5, true, nil, "a", "Ruby", obj].inspect
+  end
+end
diff --git a/spec/ruby/core/array/count_spec.rb b/spec/ruby/core/array/count_spec.rb
new file mode 100644
index 0000000000..e778233c16
--- /dev/null
+++ b/spec/ruby/core/array/count_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#count" do
+  it "returns the number of elements" do
+    [:a, :b, :c].count.should == 3
+  end
+
+  it "returns the number of elements that equal the argument" do
+    [:a, :b, :b, :c].count(:b).should == 2
+  end
+
+  it "returns the number of element for which the block evaluates to true" do
+    [:a, :b, :c].count { |s| s != :b }.should == 2
+  end
+
+  it "ignores the block if there is an argument" do
+    -> {
+      [:a, :b, :b, :c].count(:b) { |e| e.size > 10 }.should == 2
+    }.should complain(/given block not used/)
+  end
+
+  context "when a block argument given" do
+    it_behaves_like :array_iterable_and_tolerating_size_increasing, :count
+  end
+end
diff --git a/spec/ruby/core/array/cycle_spec.rb b/spec/ruby/core/array/cycle_spec.rb
new file mode 100644
index 0000000000..29284257e9
--- /dev/null
+++ b/spec/ruby/core/array/cycle_spec.rb
@@ -0,0 +1,101 @@
+require_relative '../../spec_helper'
+require_relative '../enumerable/shared/enumeratorized'
+
+describe "Array#cycle" do
+  before :each do
+    ScratchPad.record []
+
+    @array = [1, 2, 3]
+    @prc = -> x { ScratchPad << x }
+  end
+
+  it "does not yield and returns nil when the array is empty and passed value is an integer" do
+    [].cycle(6, &@prc).should == nil
+    ScratchPad.recorded.should == []
+  end
+
+  it "does not yield and returns nil when the array is empty and passed value is nil" do
+    [].cycle(nil, &@prc).should == nil
+    ScratchPad.recorded.should == []
+  end
+
+  it "does not yield and returns nil when passed 0" do
+    @array.cycle(0, &@prc).should == nil
+    ScratchPad.recorded.should == []
+  end
+
+  it "iterates the array 'count' times yielding each item to the block" do
+    @array.cycle(2, &@prc)
+    ScratchPad.recorded.should == [1, 2, 3, 1, 2, 3]
+  end
+
+  it "iterates indefinitely when not passed a count" do
+    @array.cycle do |x|
+      ScratchPad << x
+      break if ScratchPad.recorded.size > 7
+    end
+    ScratchPad.recorded.should == [1, 2, 3, 1, 2, 3, 1, 2]
+  end
+
+  it "iterates indefinitely when passed nil" do
+    @array.cycle(nil) do |x|
+      ScratchPad << x
+      break if ScratchPad.recorded.size > 7
+    end
+    ScratchPad.recorded.should == [1, 2, 3, 1, 2, 3, 1, 2]
+  end
+
+  it "does not rescue StopIteration when not passed a count" do
+    -> do
+      @array.cycle { raise StopIteration }
+    end.should.raise(StopIteration)
+  end
+
+  it "does not rescue StopIteration when passed a count" do
+    -> do
+      @array.cycle(3) { raise StopIteration }
+    end.should.raise(StopIteration)
+  end
+
+  it "iterates the array Integer(count) times when passed a Float count" do
+    @array.cycle(2.7, &@prc)
+    ScratchPad.recorded.should == [1, 2, 3, 1, 2, 3]
+  end
+
+  it "calls #to_int to convert count to an Integer" do
+    count = mock("cycle count 2")
+    count.should_receive(:to_int).and_return(2)
+
+    @array.cycle(count, &@prc)
+    ScratchPad.recorded.should == [1, 2, 3, 1, 2, 3]
+  end
+
+  it "raises a TypeError if #to_int does not return an Integer" do
+    count = mock("cycle count 2")
+    count.should_receive(:to_int).and_return("2")
+
+    -> { @array.cycle(count, &@prc) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed a String" do
+    -> { @array.cycle("4") { } }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed an Object" do
+    -> { @array.cycle(mock("cycle count")) { } }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed true" do
+    -> { @array.cycle(true) { } }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed false" do
+    -> { @array.cycle(false) { } }.should.raise(TypeError)
+  end
+
+  before :all do
+    @object = [1, 2, 3, 4]
+    @empty_object = []
+  end
+  it_should_behave_like :enumeratorized_with_cycle_size
+end
diff --git a/spec/ruby/core/array/deconstruct_spec.rb b/spec/ruby/core/array/deconstruct_spec.rb
new file mode 100644
index 0000000000..11bb8e72c4
--- /dev/null
+++ b/spec/ruby/core/array/deconstruct_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+
+describe "Array#deconstruct" do
+  it "returns self" do
+    array = [1]
+
+    array.deconstruct.should.equal? array
+  end
+end
diff --git a/spec/ruby/core/array/delete_at_spec.rb b/spec/ruby/core/array/delete_at_spec.rb
new file mode 100644
index 0000000000..1e298b6730
--- /dev/null
+++ b/spec/ruby/core/array/delete_at_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#delete_at" do
+  it "removes the element at the specified index" do
+    a = [1, 2, 3, 4]
+    a.delete_at(2)
+    a.should == [1, 2, 4]
+    a.delete_at(-1)
+    a.should == [1, 2]
+  end
+
+  it "returns the removed element at the specified index" do
+    a = [1, 2, 3, 4]
+    a.delete_at(2).should == 3
+    a.delete_at(-1).should == 4
+  end
+
+  it "returns nil and makes no modification if the index is out of range" do
+    a = [1, 2]
+    a.delete_at(3).should == nil
+    a.should == [1, 2]
+    a.delete_at(-3).should == nil
+    a.should == [1, 2]
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(-1)
+    [1, 2].delete_at(obj).should == 2
+  end
+
+  it "accepts negative indices" do
+    a = [1, 2]
+    a.delete_at(-2).should == 1
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { [1,2,3].freeze.delete_at(0) }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/delete_if_spec.rb b/spec/ruby/core/array/delete_if_spec.rb
new file mode 100644
index 0000000000..701a612395
--- /dev/null
+++ b/spec/ruby/core/array/delete_if_spec.rb
@@ -0,0 +1,82 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/enumeratorize'
+require_relative 'shared/delete_if'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+require_relative '../enumerable/shared/enumeratorized'
+
+describe "Array#delete_if" do
+  before do
+    @a = [ "a", "b", "c" ]
+  end
+
+  it "removes each element for which block returns true" do
+    @a = [ "a", "b", "c" ]
+    @a.delete_if { |x| x >= "b" }
+    @a.should == ["a"]
+  end
+
+  it "returns self" do
+    @a.delete_if{ true }.equal?(@a).should == true
+  end
+
+  it_behaves_like :enumeratorize, :delete_if
+
+  it "returns self when called on an Array emptied with #shift" do
+    array = [1]
+    array.shift
+    array.delete_if { |x| true }.should.equal?(array)
+  end
+
+  it "returns an Enumerator if no block given, and the enumerator can modify the original array" do
+    enum = @a.delete_if
+    enum.should.instance_of?(Enumerator)
+    @a.should_not.empty?
+    enum.each { true }
+    @a.should.empty?
+  end
+
+  it "returns an Enumerator if no block given, and the array is frozen" do
+    @a.freeze.delete_if.should.instance_of?(Enumerator)
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.delete_if {} }.should.raise(FrozenError)
+  end
+
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.delete_if {} }.should.raise(FrozenError)
+  end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.delete_if { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "only removes elements for which the block returns true, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.delete_if do |e|
+        case e
+        when 2 then true
+        when 3 then raise StandardError, 'Oops'
+        else false
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [1, 3, 4]
+  end
+
+  it_behaves_like :enumeratorized_with_origin_size, :delete_if, [1,2,3]
+  it_behaves_like :delete_if, :delete_if
+
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :delete_if
+end
diff --git a/spec/ruby/core/array/delete_spec.rb b/spec/ruby/core/array/delete_spec.rb
new file mode 100644
index 0000000000..0d80b2839d
--- /dev/null
+++ b/spec/ruby/core/array/delete_spec.rb
@@ -0,0 +1,46 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#delete" do
+  it "removes elements that are #== to object" do
+    x = mock('delete')
+    def x.==(other) 3 == other end
+
+    a = [1, 2, 3, x, 4, 3, 5, x]
+    a.delete mock('not contained')
+    a.should == [1, 2, 3, x, 4, 3, 5, x]
+
+    a.delete 3
+    a.should == [1, 2, 4, 5]
+  end
+
+  it "calculates equality correctly for reference values" do
+    a = ["foo", "bar", "foo", "quux", "foo"]
+    a.delete "foo"
+    a.should == ["bar","quux"]
+  end
+
+  it "returns object or nil if no elements match object" do
+    [1, 2, 4, 5].delete(1).should == 1
+    [1, 2, 4, 5].delete(3).should == nil
+  end
+
+  it "may be given a block that is executed if no element matches object" do
+    [1].delete(1) {:not_found}.should == 1
+    [].delete('a') {:not_found}.should == :not_found
+  end
+
+  it "returns nil if the array is empty due to a shift" do
+    a = [1]
+    a.shift
+    a.delete(nil).should == nil
+  end
+
+  it "returns nil on a frozen array if a modification does not take place" do
+    [1, 2, 3].freeze.delete(0).should == nil
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { [1, 2, 3].freeze.delete(1) }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/difference_spec.rb b/spec/ruby/core/array/difference_spec.rb
new file mode 100644
index 0000000000..63e32feca0
--- /dev/null
+++ b/spec/ruby/core/array/difference_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/difference'
+
+describe "Array#difference" do
+  it_behaves_like :array_binary_difference, :difference
+
+  it "returns a copy when called without any parameter" do
+    x = [1, 2, 3, 2]
+    x.difference.should == x
+    x.difference.should_not.equal? x
+  end
+
+  it "does not return subclass instances for Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3].difference.should.instance_of?(Array)
+  end
+
+  it "accepts multiple arguments" do
+    x = [1, 2, 3, 1]
+    x.difference([], [0, 1], [3, 4], [3]).should == [2]
+  end
+end
diff --git a/spec/ruby/core/array/dig_spec.rb b/spec/ruby/core/array/dig_spec.rb
new file mode 100644
index 0000000000..4166ff9f1f
--- /dev/null
+++ b/spec/ruby/core/array/dig_spec.rb
@@ -0,0 +1,52 @@
+require_relative '../../spec_helper'
+
+describe "Array#dig" do
+
+  it "returns #at with one arg" do
+    ['a'].dig(0).should == 'a'
+    ['a'].dig(1).should == nil
+  end
+
+  it "recurses array elements" do
+    a = [ [ 1, [2, '3'] ] ]
+    a.dig(0, 0).should == 1
+    a.dig(0, 1, 1).should == '3'
+    a.dig(0, -1, 0).should == 2
+  end
+
+  it "returns the nested value specified if the sequence includes a key" do
+    a = [42, { foo: :bar }]
+    a.dig(1, :foo).should == :bar
+  end
+
+  it "raises a TypeError for a non-numeric index" do
+    -> {
+      ['a'].dig(:first)
+    }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if any intermediate step does not respond to #dig" do
+    a = [1, 2]
+    -> {
+      a.dig(0, 1)
+    }.should.raise(TypeError)
+  end
+
+  it "raises an ArgumentError if no arguments provided" do
+    -> {
+      [10].dig()
+    }.should.raise(ArgumentError)
+  end
+
+  it "returns nil if any intermediate step is nil" do
+    a = [[1, [2, 3]]]
+    a.dig(1, 2, 3).should == nil
+  end
+
+  it "calls #dig on the result of #at with the remaining arguments" do
+    h = [[nil, [nil, nil, 42]]]
+    h[0].should_receive(:dig).with(1, 2).and_return(42)
+    h.dig(0, 1, 2).should == 42
+  end
+
+end
diff --git a/spec/ruby/core/array/drop_spec.rb b/spec/ruby/core/array/drop_spec.rb
new file mode 100644
index 0000000000..c0e1c9edce
--- /dev/null
+++ b/spec/ruby/core/array/drop_spec.rb
@@ -0,0 +1,56 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#drop" do
+  it "removes the specified number of elements from the start of the array" do
+    [1, 2, 3, 4, 5].drop(2).should == [3, 4, 5]
+  end
+
+  it "raises an ArgumentError if the number of elements specified is negative" do
+    -> { [1, 2].drop(-3) }.should.raise(ArgumentError)
+  end
+
+  it "returns an empty Array if all elements are dropped" do
+    [1, 2].drop(2).should == []
+  end
+
+  it "returns an empty Array when called on an empty Array" do
+    [].drop(0).should == []
+  end
+
+  it "does not remove any elements when passed zero" do
+    [1, 2].drop(0).should == [1, 2]
+  end
+
+  it "returns an empty Array if more elements than exist are dropped" do
+    [1, 2].drop(3).should == []
+  end
+
+  it 'acts correctly after a shift' do
+    ary = [nil, 1, 2]
+    ary.shift
+    ary.drop(1).should == [2]
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(2)
+
+    [1, 2, 3].drop(obj).should == [3]
+  end
+
+  it "raises a TypeError when the passed argument can't be coerced to Integer" do
+    -> { [1, 2].drop("cat") }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError when the passed argument isn't an integer and #to_int returns non-Integer" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return("cat")
+
+    -> { [1, 2].drop(obj) }.should.raise(TypeError)
+  end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].drop(1).should.instance_of?(Array)
+  end
+end
diff --git a/spec/ruby/core/array/drop_while_spec.rb b/spec/ruby/core/array/drop_while_spec.rb
new file mode 100644
index 0000000000..4fead3ff06
--- /dev/null
+++ b/spec/ruby/core/array/drop_while_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#drop_while" do
+  @value_to_return = -> _ { true }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :drop_while
+
+  it "removes elements from the start of the array while the block evaluates to true" do
+    [1, 2, 3, 4].drop_while { |n| n < 4 }.should == [4]
+  end
+
+  it "removes elements from the start of the array until the block returns nil" do
+    [1, 2, 3, nil, 5].drop_while { |n| n }.should == [nil, 5]
+  end
+
+  it "removes elements from the start of the array until the block returns false" do
+    [1, 2, 3, false, 5].drop_while { |n| n }.should == [false, 5]
+  end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].drop_while { |n| n < 4 }.should.instance_of?(Array)
+  end
+end
diff --git a/spec/ruby/core/array/dup_spec.rb b/spec/ruby/core/array/dup_spec.rb
new file mode 100644
index 0000000000..f14aeca3b5
--- /dev/null
+++ b/spec/ruby/core/array/dup_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/clone'
+
+describe "Array#dup" do
+  it_behaves_like :array_clone, :dup # FIX: no, clone and dup are not alike
+
+  it "does not copy frozen status from the original" do
+    a = [1, 2, 3, 4]
+    b = [1, 2, 3, 4]
+    a.freeze
+    aa = a.dup
+    bb = b.dup
+
+    aa.frozen?.should == false
+    bb.frozen?.should == false
+  end
+
+  it "does not copy singleton methods" do
+    a = [1, 2, 3, 4]
+    b = [1, 2, 3, 4]
+    def a.a_singleton_method; end
+    aa = a.dup
+    bb = b.dup
+
+    a.respond_to?(:a_singleton_method).should == true
+    b.respond_to?(:a_singleton_method).should == false
+    aa.respond_to?(:a_singleton_method).should == false
+    bb.respond_to?(:a_singleton_method).should == false
+  end
+end
diff --git a/spec/ruby/core/array/each_index_spec.rb b/spec/ruby/core/array/each_index_spec.rb
new file mode 100644
index 0000000000..b238a89d8a
--- /dev/null
+++ b/spec/ruby/core/array/each_index_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/enumeratorize'
+require_relative '../enumerable/shared/enumeratorized'
+
+# Modifying a collection while the contents are being iterated
+# gives undefined behavior. See
+# https://blade.ruby-lang.org/ruby-core/23633
+
+describe "Array#each_index" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  it "passes the index of each element to the block" do
+    a = ['a', 'b', 'c', 'd']
+    a.each_index { |i| ScratchPad << i }
+    ScratchPad.recorded.should == [0, 1, 2, 3]
+  end
+
+  it "returns self" do
+    a = [:a, :b, :c]
+    a.each_index { |i| }.should.equal?(a)
+  end
+
+  it "is not confused by removing elements from the front" do
+    a = [1, 2, 3]
+
+    a.shift
+    ScratchPad.record []
+    a.each_index { |i| ScratchPad << i }
+    ScratchPad.recorded.should == [0, 1]
+
+    a.shift
+    ScratchPad.record []
+    a.each_index { |i| ScratchPad << i }
+    ScratchPad.recorded.should == [0]
+  end
+
+  it_behaves_like :enumeratorize, :each_index
+  it_behaves_like :enumeratorized_with_origin_size, :each_index, [1,2,3]
+end
+
+describe "Array#each_index" do
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.each_index do |index|
+      ScratchPad << index
+      array << i if i < 100
+      i += 1
+    end
+
+    ScratchPad.recorded.should == (0..102).to_a # element indices
+  end
+end
diff --git a/spec/ruby/core/array/each_spec.rb b/spec/ruby/core/array/each_spec.rb
new file mode 100644
index 0000000000..73a4c36b17
--- /dev/null
+++ b/spec/ruby/core/array/each_spec.rb
@@ -0,0 +1,82 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/enumeratorize'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+require_relative '../enumerable/shared/enumeratorized'
+
+# Mutating the array while it is being iterated is discouraged as it can result in confusing behavior.
+# Yet a Ruby implementation must not crash in such a case, and following the simple CRuby behavior makes sense.
+# CRuby simply reads the array storage and checks the size for every iteration;
+# like `i = 0; while i < size; yield self[i]; i += 1; end`
+
+describe "Array#each" do
+  it "yields each element to the block" do
+    a = []
+    x = [1, 2, 3]
+    x.each { |item| a << item }.should.equal?(x)
+    a.should == [1, 2, 3]
+  end
+
+  it "yields each element to the block even if the array is changed during iteration" do
+    a = [1, 2, 3, 4, 5]
+    iterated = []
+    a.each { |x| iterated << x; a << x+5 if x.even? }
+    iterated.should == [1, 2, 3, 4, 5, 7, 9]
+  end
+
+  it "yields only elements that are still in the array" do
+    a = [0, 1, 2, 3, 4]
+    iterated = []
+    a.each { |x| iterated << x; a.pop if x.even? }
+    iterated.should == [0, 1, 2]
+  end
+
+  it "yields elements based on an internal index" do
+    a = [0, 1, 2, 3, 4]
+    iterated = []
+    a.each { |x| iterated << x; a.shift if x.even? }
+    iterated.should == [0, 2, 4]
+  end
+
+  it "yields the same element multiple times if inserting while iterating" do
+    a = [1, 2]
+    iterated = []
+    a.each { |x| iterated << x; a.unshift(0) if a.size == 2 }
+    iterated.should == [1, 1, 2]
+  end
+
+  it "yields each element to a block that takes multiple arguments" do
+    a = [[1, 2], :a, [3, 4]]
+    b = []
+
+    a.each { |x, y| b << x }
+    b.should == [1, :a, 3]
+
+    b = []
+    a.each { |x, y| b << y }
+    b.should == [2, nil, 4]
+  end
+
+  it "yields elements added to the end of the array by the block" do
+    a = [2]
+    iterated = []
+    a.each { |x| iterated << x; x.times { a << 0 } }
+
+    iterated.should == [2, 0, 0]
+  end
+
+  it "does not yield elements deleted from the end of the array" do
+    a = [2, 3, 1]
+    iterated = []
+    a.each { |x| iterated << x; a.delete_at(2) if x == 3 }
+
+    iterated.should == [2, 3]
+  end
+
+  it_behaves_like :enumeratorize, :each
+  it_behaves_like :enumeratorized_with_origin_size, :each, [1,2,3]
+end
+
+describe "Array#each" do
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :each
+end
diff --git a/spec/ruby/core/array/element_reference_spec.rb b/spec/ruby/core/array/element_reference_spec.rb
new file mode 100644
index 0000000000..d5f4b54961
--- /dev/null
+++ b/spec/ruby/core/array/element_reference_spec.rb
@@ -0,0 +1,903 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#[]" do
+  it "returns the element at index with [index]" do
+    [ "a", "b", "c", "d", "e" ][1].should == "b"
+
+    a = [1, 2, 3, 4]
+
+    a[0].should == 1
+    a[1].should == 2
+    a[2].should == 3
+    a[3].should == 4
+    a[4].should == nil
+    a[10].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns the element at index from the end of the array with [-index]" do
+    [ "a", "b", "c", "d", "e" ][-2].should == "d"
+
+    a = [1, 2, 3, 4]
+
+    a[-1].should == 4
+    a[-2].should == 3
+    a[-3].should == 2
+    a[-4].should == 1
+    a[-5].should == nil
+    a[-10].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns count elements starting from index with [index, count]" do
+    [ "a", "b", "c", "d", "e" ][2, 3].should == ["c", "d", "e"]
+
+    a = [1, 2, 3, 4]
+
+    a[0, 0].should == []
+    a[0, 1].should == [1]
+    a[0, 2].should == [1, 2]
+    a[0, 4].should == [1, 2, 3, 4]
+    a[0, 6].should == [1, 2, 3, 4]
+    a[0, -1].should == nil
+    a[0, -2].should == nil
+    a[0, -4].should == nil
+
+    a[2, 0].should == []
+    a[2, 1].should == [3]
+    a[2, 2].should == [3, 4]
+    a[2, 4].should == [3, 4]
+    a[2, -1].should == nil
+
+    a[4, 0].should == []
+    a[4, 2].should == []
+    a[4, -1].should == nil
+
+    a[5, 0].should == nil
+    a[5, 2].should == nil
+    a[5, -1].should == nil
+
+    a[6, 0].should == nil
+    a[6, 2].should == nil
+    a[6, -1].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns count elements starting at index from the end of array with [-index, count]" do
+    [ "a", "b", "c", "d", "e" ][-2, 2].should == ["d", "e"]
+
+    a = [1, 2, 3, 4]
+
+    a[-1, 0].should == []
+    a[-1, 1].should == [4]
+    a[-1, 2].should == [4]
+    a[-1, -1].should == nil
+
+    a[-2, 0].should == []
+    a[-2, 1].should == [3]
+    a[-2, 2].should == [3, 4]
+    a[-2, 4].should == [3, 4]
+    a[-2, -1].should == nil
+
+    a[-4, 0].should == []
+    a[-4, 1].should == [1]
+    a[-4, 2].should == [1, 2]
+    a[-4, 4].should == [1, 2, 3, 4]
+    a[-4, 6].should == [1, 2, 3, 4]
+    a[-4, -1].should == nil
+
+    a[-5, 0].should == nil
+    a[-5, 1].should == nil
+    a[-5, 10].should == nil
+    a[-5, -1].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns the first count elements with [0, count]" do
+    [ "a", "b", "c", "d", "e" ][0, 3].should == ["a", "b", "c"]
+  end
+
+  it "returns the subarray which is independent to self with [index,count]" do
+    a = [1, 2, 3]
+    sub = a[1, 2]
+    sub.replace([:a, :b])
+    a.should == [1, 2, 3]
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.stub!(:to_int).and_return(2)
+
+    a = [1, 2, 3, 4]
+    a[obj].should == 3
+    a[obj, 1].should == [3]
+    a[obj, obj].should == [3, 4]
+    a[0, obj].should == [1, 2]
+  end
+
+  it "raises TypeError if to_int returns non-integer" do
+    from = mock('from')
+    to = mock('to')
+
+    # So we can construct a range out of them...
+    def from.<=>(o) 0 end
+    def to.<=>(o) 0 end
+
+    a = [1, 2, 3, 4, 5]
+
+    def from.to_int() 'cat' end
+    def to.to_int() -2 end
+
+    -> { a[from..to] }.should.raise(TypeError)
+
+    def from.to_int() 1 end
+    def to.to_int() 'cat' end
+
+    -> { a[from..to] }.should.raise(TypeError)
+  end
+
+  it "returns the elements specified by Range indexes with [m..n]" do
+    [ "a", "b", "c", "d", "e" ][1..3].should == ["b", "c", "d"]
+    [ "a", "b", "c", "d", "e" ][4..-1].should == ['e']
+    [ "a", "b", "c", "d", "e" ][3..3].should == ['d']
+    [ "a", "b", "c", "d", "e" ][3..-2].should == ['d']
+    ['a'][0..-1].should == ['a']
+
+    a = [1, 2, 3, 4]
+
+    a[0..-10].should == []
+    a[0..0].should == [1]
+    a[0..1].should == [1, 2]
+    a[0..2].should == [1, 2, 3]
+    a[0..3].should == [1, 2, 3, 4]
+    a[0..4].should == [1, 2, 3, 4]
+    a[0..10].should == [1, 2, 3, 4]
+
+    a[2..-10].should == []
+    a[2..0].should == []
+    a[2..2].should == [3]
+    a[2..3].should == [3, 4]
+    a[2..4].should == [3, 4]
+
+    a[3..0].should == []
+    a[3..3].should == [4]
+    a[3..4].should == [4]
+
+    a[4..0].should == []
+    a[4..4].should == []
+    a[4..5].should == []
+
+    a[5..0].should == nil
+    a[5..5].should == nil
+    a[5..6].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns elements specified by Range indexes except the element at index n with [m...n]" do
+    [ "a", "b", "c", "d", "e" ][1...3].should == ["b", "c"]
+
+    a = [1, 2, 3, 4]
+
+    a[0...-10].should == []
+    a[0...0].should == []
+    a[0...1].should == [1]
+    a[0...2].should == [1, 2]
+    a[0...3].should == [1, 2, 3]
+    a[0...4].should == [1, 2, 3, 4]
+    a[0...10].should == [1, 2, 3, 4]
+
+    a[2...-10].should == []
+    a[2...0].should == []
+    a[2...2].should == []
+    a[2...3].should == [3]
+    a[2...4].should == [3, 4]
+
+    a[3...0].should == []
+    a[3...3].should == []
+    a[3...4].should == [4]
+
+    a[4...0].should == []
+    a[4...4].should == []
+    a[4...5].should == []
+
+    a[5...0].should == nil
+    a[5...5].should == nil
+    a[5...6].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns elements that exist if range start is in the array but range end is not with [m..n]" do
+    [ "a", "b", "c", "d", "e" ][4..7].should == ["e"]
+  end
+
+  it "accepts Range instances having a negative m and both signs for n with [m..n] and [m...n]" do
+    a = [1, 2, 3, 4]
+
+    a[-1..-1].should == [4]
+    a[-1...-1].should == []
+    a[-1..3].should == [4]
+    a[-1...3].should == []
+    a[-1..4].should == [4]
+    a[-1...4].should == [4]
+    a[-1..10].should == [4]
+    a[-1...10].should == [4]
+    a[-1..0].should == []
+    a[-1..-4].should == []
+    a[-1...-4].should == []
+    a[-1..-6].should == []
+    a[-1...-6].should == []
+
+    a[-2..-2].should == [3]
+    a[-2...-2].should == []
+    a[-2..-1].should == [3, 4]
+    a[-2...-1].should == [3]
+    a[-2..10].should == [3, 4]
+    a[-2...10].should == [3, 4]
+
+    a[-4..-4].should == [1]
+    a[-4..-2].should == [1, 2, 3]
+    a[-4...-2].should == [1, 2]
+    a[-4..-1].should == [1, 2, 3, 4]
+    a[-4...-1].should == [1, 2, 3]
+    a[-4..3].should == [1, 2, 3, 4]
+    a[-4...3].should == [1, 2, 3]
+    a[-4..4].should == [1, 2, 3, 4]
+    a[-4...4].should == [1, 2, 3, 4]
+    a[-4...4].should == [1, 2, 3, 4]
+    a[-4..0].should == [1]
+    a[-4...0].should == []
+    a[-4..1].should == [1, 2]
+    a[-4...1].should == [1]
+
+    a[-5..-5].should == nil
+    a[-5...-5].should == nil
+    a[-5..-4].should == nil
+    a[-5..-1].should == nil
+    a[-5..10].should == nil
+
+    a.should == [1, 2, 3, 4]
+  end
+
+  it "returns the subarray which is independent to self with [m..n]" do
+    a = [1, 2, 3]
+    sub = a[1..2]
+    sub.replace([:a, :b])
+    a.should == [1, 2, 3]
+  end
+
+  it "tries to convert Range elements to Integers using #to_int with [m..n] and [m...n]" do
+    from = mock('from')
+    to = mock('to')
+
+    # So we can construct a range out of them...
+    def from.<=>(o) 0 end
+    def to.<=>(o) 0 end
+
+    def from.to_int() 1 end
+    def to.to_int() -2 end
+
+    a = [1, 2, 3, 4]
+
+    a[from..to].should == [2, 3]
+    a[from...to].should == [2]
+    a[1..0].should == []
+    a[1...0].should == []
+
+    -> { a["a" .. "b"] }.should.raise(TypeError)
+    -> { a["a" ... "b"] }.should.raise(TypeError)
+    -> { a[from .. "b"] }.should.raise(TypeError)
+    -> { a[from ... "b"] }.should.raise(TypeError)
+  end
+
+  it "returns the same elements as [m..n] and [m...n] with Range subclasses" do
+    a = [1, 2, 3, 4]
+    range_incl = ArraySpecs::MyRange.new(1, 2)
+    range_excl = ArraySpecs::MyRange.new(-3, -1, true)
+
+    a[range_incl].should == [2, 3]
+    a[range_excl].should == [2, 3]
+  end
+
+  it "returns nil for a requested index not in the array with [index]" do
+    [ "a", "b", "c", "d", "e" ][5].should == nil
+  end
+
+  it "returns [] if the index is valid but length is zero with [index, length]" do
+    [ "a", "b", "c", "d", "e" ][0, 0].should == []
+    [ "a", "b", "c", "d", "e" ][2, 0].should == []
+  end
+
+  it "returns nil if length is zero but index is invalid with [index, length]" do
+    [ "a", "b", "c", "d", "e" ][100, 0].should == nil
+    [ "a", "b", "c", "d", "e" ][-50, 0].should == nil
+  end
+
+  # This is by design. It is in the official documentation.
+  it "returns [] if index == array.size with [index, length]" do
+    %w|a b c d e|[5, 2].should == []
+  end
+
+  it "returns nil if index > array.size with [index, length]" do
+    %w|a b c d e|[6, 2].should == nil
+  end
+
+  it "returns nil if length is negative with [index, length]" do
+    %w|a b c d e|[3, -1].should == nil
+    %w|a b c d e|[2, -2].should == nil
+    %w|a b c d e|[1, -100].should == nil
+  end
+
+  it "returns nil if no requested index is in the array with [m..n]" do
+    [ "a", "b", "c", "d", "e" ][6..10].should == nil
+  end
+
+  it "returns nil if range start is not in the array with [m..n]" do
+    [ "a", "b", "c", "d", "e" ][-10..2].should == nil
+    [ "a", "b", "c", "d", "e" ][10..12].should == nil
+  end
+
+  it "returns an empty array when m == n with [m...n]" do
+    [1, 2, 3, 4, 5][1...1].should == []
+  end
+
+  it "returns an empty array with [0...0]" do
+    [1, 2, 3, 4, 5][0...0].should == []
+  end
+
+  it "returns a subarray where m, n negatives and m < n with [m..n]" do
+    [ "a", "b", "c", "d", "e" ][-3..-2].should == ["c", "d"]
+  end
+
+  it "returns an array containing the first element with [0..0]" do
+    [1, 2, 3, 4, 5][0..0].should == [1]
+  end
+
+  it "returns the entire array with [0..-1]" do
+    [1, 2, 3, 4, 5][0..-1].should == [1, 2, 3, 4, 5]
+  end
+
+  it "returns all but the last element with [0...-1]" do
+    [1, 2, 3, 4, 5][0...-1].should == [1, 2, 3, 4]
+  end
+
+  it "returns [3] for [2..-1] out of [1, 2, 3]" do
+    [1,2,3][2..-1].should == [3]
+  end
+
+  it "returns an empty array when m > n and m, n are positive with [m..n]" do
+    [1, 2, 3, 4, 5][3..2].should == []
+  end
+
+  it "returns an empty array when m > n and m, n are negative with [m..n]" do
+    [1, 2, 3, 4, 5][-2..-3].should == []
+  end
+
+  it "does not expand array when the indices are outside of the array bounds" do
+    a = [1, 2]
+    a[4].should == nil
+    a.should == [1, 2]
+    a[4, 0].should == nil
+    a.should == [1, 2]
+    a[6, 1].should == nil
+    a.should == [1, 2]
+    a[8...8].should == nil
+    a.should == [1, 2]
+    a[10..10].should == nil
+    a.should == [1, 2]
+  end
+
+  describe "with a subclass of Array" do
+    before :each do
+      ScratchPad.clear
+
+      @array = ArraySpecs::MyArray[1, 2, 3, 4, 5]
+    end
+
+    it "returns a Array instance with [n, m]" do
+      @array[0, 2].should.instance_of?(Array)
+    end
+
+    it "returns a Array instance with [-n, m]" do
+      @array[-3, 2].should.instance_of?(Array)
+    end
+
+    it "returns a Array instance with [n..m]" do
+      @array[1..3].should.instance_of?(Array)
+    end
+
+    it "returns a Array instance with [n...m]" do
+      @array[1...3].should.instance_of?(Array)
+    end
+
+    it "returns a Array instance with [-n..-m]" do
+      @array[-3..-1].should.instance_of?(Array)
+    end
+
+    it "returns a Array instance with [-n...-m]" do
+      @array[-3...-1].should.instance_of?(Array)
+    end
+
+    it "returns an empty array when m == n with [m...n]" do
+      @array[1...1].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "returns an empty array with [0...0]" do
+      @array[0...0].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "returns an empty array when m > n and m, n are positive with [m..n]" do
+      @array[3..2].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "returns an empty array when m > n and m, n are negative with [m..n]" do
+      @array[-2..-3].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "returns [] if index == array.size with [index, length]" do
+      @array[5, 2].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "returns [] if the index is valid but length is zero with [index, length]" do
+      @array[0, 0].should == []
+      @array[2, 0].should == []
+      ScratchPad.recorded.should == nil
+    end
+
+    it "does not call #initialize on the subclass instance" do
+      @array[0, 3].should == [1, 2, 3]
+      ScratchPad.recorded.should == nil
+    end
+  end
+
+  it "raises a RangeError when the start index is out of range of Fixnum" do
+    array = [1, 2, 3, 4, 5, 6]
+    obj = mock('large value')
+    obj.should_receive(:to_int).and_return(bignum_value)
+    -> { array[obj] }.should.raise(RangeError)
+
+    obj = 8e19
+    -> { array[obj] }.should.raise(RangeError)
+
+    # boundary value when longs are 64 bits
+    -> { array[2.0**63] }.should.raise(RangeError)
+
+    # just under the boundary value when longs are 64 bits
+    array[max_long.to_f.prev_float].should == nil
+  end
+
+  it "raises a RangeError when the length is out of range of Fixnum" do
+    array = [1, 2, 3, 4, 5, 6]
+    obj = mock('large value')
+    obj.should_receive(:to_int).and_return(bignum_value)
+    -> { array[1, obj] }.should.raise(RangeError)
+
+    obj = 8e19
+    -> { array[1, obj] }.should.raise(RangeError)
+  end
+
+  it "raises a type error if a range is passed with a length" do
+    ->{ [1, 2, 3][1..2, 1] }.should.raise(TypeError)
+  end
+
+  it "raises a RangeError if passed a range with a bound that is too large" do
+    array = [1, 2, 3, 4, 5, 6]
+    -> { array[bignum_value..(bignum_value + 1)] }.should.raise(RangeError)
+    -> { array[0..bignum_value] }.should.raise(RangeError)
+  end
+
+  it "can accept endless ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a[eval("(2..)")].should == [2, 3, 4, 5]
+    a[eval("(2...)")].should == [2, 3, 4, 5]
+    a[eval("(-2..)")].should == [4, 5]
+    a[eval("(-2...)")].should == [4, 5]
+    a[eval("(9..)")].should == nil
+    a[eval("(9...)")].should == nil
+    a[eval("(-9..)")].should == nil
+    a[eval("(-9...)")].should == nil
+  end
+
+  describe "can be sliced with Enumerator::ArithmeticSequence" do
+    before :each do
+      @array = [0, 1, 2, 3, 4, 5]
+    end
+
+    it "has endless range and positive steps" do
+      @array[eval("(0..).step(1)")].should == [0, 1, 2, 3, 4, 5]
+      @array[eval("(0..).step(2)")].should == [0, 2, 4]
+      @array[eval("(0..).step(10)")].should == [0]
+
+      @array[eval("(2..).step(1)")].should == [2, 3, 4, 5]
+      @array[eval("(2..).step(2)")].should == [2, 4]
+      @array[eval("(2..).step(10)")].should == [2]
+
+      @array[eval("(-3..).step(1)")].should == [3, 4, 5]
+      @array[eval("(-3..).step(2)")].should == [3, 5]
+      @array[eval("(-3..).step(10)")].should == [3]
+    end
+
+    it "has beginless range and positive steps" do
+      # end with zero index
+      @array[(..0).step(1)].should == [0]
+      @array[(...0).step(1)].should == []
+
+      @array[(..0).step(2)].should == [0]
+      @array[(...0).step(2)].should == []
+
+      @array[(..0).step(10)].should == [0]
+      @array[(...0).step(10)].should == []
+
+      # end with positive index
+      @array[(..3).step(1)].should == [0, 1, 2, 3]
+      @array[(...3).step(1)].should == [0, 1, 2]
+
+      @array[(..3).step(2)].should == [0, 2]
+      @array[(...3).step(2)].should == [0, 2]
+
+      @array[(..3).step(10)].should == [0]
+      @array[(...3).step(10)].should == [0]
+
+      # end with negative index
+      @array[(..-2).step(1)].should == [0, 1, 2, 3, 4,]
+      @array[(...-2).step(1)].should == [0, 1, 2, 3]
+
+      @array[(..-2).step(2)].should == [0, 2, 4]
+      @array[(...-2).step(2)].should == [0, 2]
+
+      @array[(..-2).step(10)].should == [0]
+      @array[(...-2).step(10)].should == [0]
+    end
+
+    it "has endless range and negative steps" do
+      @array[eval("(0..).step(-1)")].should == [0]
+      @array[eval("(0..).step(-2)")].should == [0]
+      @array[eval("(0..).step(-10)")].should == [0]
+
+      @array[eval("(2..).step(-1)")].should == [2, 1, 0]
+      @array[eval("(2..).step(-2)")].should == [2, 0]
+
+      @array[eval("(-3..).step(-1)")].should == [3, 2, 1, 0]
+      @array[eval("(-3..).step(-2)")].should == [3, 1]
+    end
+
+    it "has closed range and positive steps" do
+      # start and end with 0
+      @array[eval("(0..0).step(1)")].should == [0]
+      @array[eval("(0...0).step(1)")].should == []
+
+      @array[eval("(0..0).step(2)")].should == [0]
+      @array[eval("(0...0).step(2)")].should == []
+
+      @array[eval("(0..0).step(10)")].should == [0]
+      @array[eval("(0...0).step(10)")].should == []
+
+      # start and end with positive index
+      @array[eval("(1..3).step(1)")].should == [1, 2, 3]
+      @array[eval("(1...3).step(1)")].should == [1, 2]
+
+      @array[eval("(1..3).step(2)")].should == [1, 3]
+      @array[eval("(1...3).step(2)")].should == [1]
+
+      @array[eval("(1..3).step(10)")].should == [1]
+      @array[eval("(1...3).step(10)")].should == [1]
+
+      # start with positive index, end with negative index
+      @array[eval("(1..-2).step(1)")].should == [1, 2, 3, 4]
+      @array[eval("(1...-2).step(1)")].should == [1, 2, 3]
+
+      @array[eval("(1..-2).step(2)")].should ==  [1, 3]
+      @array[eval("(1...-2).step(2)")].should ==  [1, 3]
+
+      @array[eval("(1..-2).step(10)")].should == [1]
+      @array[eval("(1...-2).step(10)")].should == [1]
+
+      # start with negative index, end with positive index
+      @array[eval("(-4..4).step(1)")].should == [2, 3, 4]
+      @array[eval("(-4...4).step(1)")].should == [2, 3]
+
+      @array[eval("(-4..4).step(2)")].should == [2, 4]
+      @array[eval("(-4...4).step(2)")].should == [2]
+
+      @array[eval("(-4..4).step(10)")].should == [2]
+      @array[eval("(-4...4).step(10)")].should == [2]
+
+      # start with negative index, end with negative index
+      @array[eval("(-4..-2).step(1)")].should == [2, 3, 4]
+      @array[eval("(-4...-2).step(1)")].should == [2, 3]
+
+      @array[eval("(-4..-2).step(2)")].should == [2, 4]
+      @array[eval("(-4...-2).step(2)")].should == [2]
+
+      @array[eval("(-4..-2).step(10)")].should == [2]
+      @array[eval("(-4...-2).step(10)")].should == [2]
+    end
+
+    it "has closed range and negative steps" do
+      # start and end with 0
+      @array[eval("(0..0).step(-1)")].should == [0]
+      @array[eval("(0...0).step(-1)")].should == []
+
+      @array[eval("(0..0).step(-2)")].should == [0]
+      @array[eval("(0...0).step(-2)")].should == []
+
+      @array[eval("(0..0).step(-10)")].should == [0]
+      @array[eval("(0...0).step(-10)")].should == []
+
+      # start and end with positive index
+      @array[eval("(1..3).step(-1)")].should == []
+      @array[eval("(1...3).step(-1)")].should == []
+
+      @array[eval("(1..3).step(-2)")].should == []
+      @array[eval("(1...3).step(-2)")].should == []
+
+      @array[eval("(1..3).step(-10)")].should == []
+      @array[eval("(1...3).step(-10)")].should == []
+
+      # start with positive index, end with negative index
+      @array[eval("(1..-2).step(-1)")].should == []
+      @array[eval("(1...-2).step(-1)")].should == []
+
+      @array[eval("(1..-2).step(-2)")].should ==  []
+      @array[eval("(1...-2).step(-2)")].should ==  []
+
+      @array[eval("(1..-2).step(-10)")].should == []
+      @array[eval("(1...-2).step(-10)")].should == []
+
+      # start with negative index, end with positive index
+      @array[eval("(-4..4).step(-1)")].should == []
+      @array[eval("(-4...4).step(-1)")].should == []
+
+      @array[eval("(-4..4).step(-2)")].should == []
+      @array[eval("(-4...4).step(-2)")].should == []
+
+      @array[eval("(-4..4).step(-10)")].should == []
+      @array[eval("(-4...4).step(-10)")].should == []
+
+      # start with negative index, end with negative index
+      @array[eval("(-4..-2).step(-1)")].should == []
+      @array[eval("(-4...-2).step(-1)")].should == []
+
+      @array[eval("(-4..-2).step(-2)")].should == []
+      @array[eval("(-4...-2).step(-2)")].should == []
+
+      @array[eval("(-4..-2).step(-10)")].should == []
+      @array[eval("(-4...-2).step(-10)")].should == []
+    end
+
+    it "has inverted closed range and positive steps" do
+      # start and end with positive index
+      @array[eval("(3..1).step(1)")].should == []
+      @array[eval("(3...1).step(1)")].should == []
+
+      @array[eval("(3..1).step(2)")].should == []
+      @array[eval("(3...1).step(2)")].should == []
+
+      @array[eval("(3..1).step(10)")].should == []
+      @array[eval("(3...1).step(10)")].should == []
+
+      # start with negative index, end with positive index
+      @array[eval("(-2..1).step(1)")].should == []
+      @array[eval("(-2...1).step(1)")].should == []
+
+      @array[eval("(-2..1).step(2)")].should ==  []
+      @array[eval("(-2...1).step(2)")].should ==  []
+
+      @array[eval("(-2..1).step(10)")].should == []
+      @array[eval("(-2...1).step(10)")].should == []
+
+      # start with positive index, end with negative index
+      @array[eval("(4..-4).step(1)")].should == []
+      @array[eval("(4...-4).step(1)")].should == []
+
+      @array[eval("(4..-4).step(2)")].should == []
+      @array[eval("(4...-4).step(2)")].should == []
+
+      @array[eval("(4..-4).step(10)")].should == []
+      @array[eval("(4...-4).step(10)")].should == []
+
+      # start with negative index, end with negative index
+      @array[eval("(-2..-4).step(1)")].should == []
+      @array[eval("(-2...-4).step(1)")].should == []
+
+      @array[eval("(-2..-4).step(2)")].should == []
+      @array[eval("(-2...-4).step(2)")].should == []
+
+      @array[eval("(-2..-4).step(10)")].should == []
+      @array[eval("(-2...-4).step(10)")].should == []
+    end
+
+    it "has range with bounds outside of array" do
+      # end is equal to array's length
+      @array[(0..6).step(1)].should == [0, 1, 2, 3, 4, 5]
+      -> { @array[(0..6).step(2)] }.should.raise(RangeError)
+
+      # end is greater than length with positive steps
+      @array[(1..6).step(2)].should == [1, 3, 5]
+      @array[(2..7).step(2)].should == [2, 4]
+      -> { @array[(2..8).step(2)] }.should.raise(RangeError)
+
+      # begin is greater than length with negative steps
+      @array[(6..1).step(-2)].should == [5, 3, 1]
+      @array[(7..2).step(-2)].should == [5, 3]
+      -> { @array[(8..2).step(-2)] }.should.raise(RangeError)
+    end
+
+    it "has endless range with start outside of array's bounds" do
+      @array[eval("(6..).step(1)")].should == []
+      @array[eval("(7..).step(1)")].should == nil
+
+      @array[eval("(6..).step(2)")].should == []
+      -> { @array[eval("(7..).step(2)")] }.should.raise(RangeError)
+    end
+  end
+
+  it "can accept beginless ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a[(..3)].should == [0, 1, 2, 3]
+    a[(...3)].should == [0, 1, 2]
+    a[(..-3)].should == [0, 1, 2, 3]
+    a[(...-3)].should == [0, 1, 2]
+    a[(..0)].should == [0]
+    a[(...0)].should == []
+    a[(..9)].should == [0, 1, 2, 3, 4, 5]
+    a[(...9)].should == [0, 1, 2, 3, 4, 5]
+    a[(..-9)].should == []
+    a[(...-9)].should == []
+  end
+
+  describe "can be sliced with Enumerator::ArithmeticSequence" do
+    it "with infinite/inverted ranges and negative steps" do
+      array = [0, 1, 2, 3, 4, 5]
+      array[(2..).step(-1)].should == [2, 1, 0]
+      array[(2..).step(-2)].should == [2, 0]
+      array[(2..).step(-3)].should == [2]
+      array[(2..).step(-4)].should == [2]
+
+      array[(-3..).step(-1)].should == [3, 2, 1, 0]
+      array[(-3..).step(-2)].should == [3, 1]
+      array[(-3..).step(-3)].should == [3, 0]
+      array[(-3..).step(-4)].should == [3]
+      array[(-3..).step(-5)].should == [3]
+
+      array[(..0).step(-1)].should == [5, 4, 3, 2, 1, 0]
+      array[(..0).step(-2)].should == [5, 3, 1]
+      array[(..0).step(-3)].should == [5, 2]
+      array[(..0).step(-4)].should == [5, 1]
+      array[(..0).step(-5)].should == [5, 0]
+      array[(..0).step(-6)].should == [5]
+      array[(..0).step(-7)].should == [5]
+
+      array[(...0).step(-1)].should == [5, 4, 3, 2, 1]
+      array[(...0).step(-2)].should == [5, 3, 1]
+      array[(...0).step(-3)].should == [5, 2]
+      array[(...0).step(-4)].should == [5, 1]
+      array[(...0).step(-5)].should == [5]
+      array[(...0).step(-6)].should == [5]
+
+      array[(...1).step(-1)].should == [5, 4, 3, 2]
+      array[(...1).step(-2)].should == [5, 3]
+      array[(...1).step(-3)].should == [5, 2]
+      array[(...1).step(-4)].should == [5]
+      array[(...1).step(-5)].should == [5]
+
+      array[(..-5).step(-1)].should == [5, 4, 3, 2, 1]
+      array[(..-5).step(-2)].should == [5, 3, 1]
+      array[(..-5).step(-3)].should == [5, 2]
+      array[(..-5).step(-4)].should == [5, 1]
+      array[(..-5).step(-5)].should == [5]
+      array[(..-5).step(-6)].should == [5]
+
+      array[(...-5).step(-1)].should == [5, 4, 3, 2]
+      array[(...-5).step(-2)].should == [5, 3]
+      array[(...-5).step(-3)].should == [5, 2]
+      array[(...-5).step(-4)].should == [5]
+      array[(...-5).step(-5)].should == [5]
+
+      array[(4..1).step(-1)].should == [4, 3, 2, 1]
+      array[(4..1).step(-2)].should == [4, 2]
+      array[(4..1).step(-3)].should == [4, 1]
+      array[(4..1).step(-4)].should == [4]
+      array[(4..1).step(-5)].should == [4]
+
+      array[(4...1).step(-1)].should == [4, 3, 2]
+      array[(4...1).step(-2)].should == [4, 2]
+      array[(4...1).step(-3)].should == [4]
+      array[(4...1).step(-4)].should == [4]
+
+      array[(-2..1).step(-1)].should == [4, 3, 2, 1]
+      array[(-2..1).step(-2)].should == [4, 2]
+      array[(-2..1).step(-3)].should == [4, 1]
+      array[(-2..1).step(-4)].should == [4]
+      array[(-2..1).step(-5)].should == [4]
+
+      array[(-2...1).step(-1)].should == [4, 3, 2]
+      array[(-2...1).step(-2)].should == [4, 2]
+      array[(-2...1).step(-3)].should == [4]
+      array[(-2...1).step(-4)].should == [4]
+
+      array[(4..-5).step(-1)].should == [4, 3, 2, 1]
+      array[(4..-5).step(-2)].should == [4, 2]
+      array[(4..-5).step(-3)].should == [4, 1]
+      array[(4..-5).step(-4)].should == [4]
+      array[(4..-5).step(-5)].should == [4]
+
+      array[(4...-5).step(-1)].should == [4, 3, 2]
+      array[(4...-5).step(-2)].should == [4, 2]
+      array[(4...-5).step(-3)].should == [4]
+      array[(4...-5).step(-4)].should == [4]
+
+      array[(-2..-5).step(-1)].should == [4, 3, 2, 1]
+      array[(-2..-5).step(-2)].should == [4, 2]
+      array[(-2..-5).step(-3)].should == [4, 1]
+      array[(-2..-5).step(-4)].should == [4]
+      array[(-2..-5).step(-5)].should == [4]
+
+      array[(-2...-5).step(-1)].should == [4, 3, 2]
+      array[(-2...-5).step(-2)].should == [4, 2]
+      array[(-2...-5).step(-3)].should == [4]
+      array[(-2...-5).step(-4)].should == [4]
+    end
+  end
+
+  it "can accept nil...nil ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a[eval("(nil...nil)")].should == a
+    a[(...nil)].should == a
+    a[eval("(nil..)")].should == a
+  end
+end
+
+describe "Array.[]" do
+  it "[] should return a new array populated with the given elements" do
+    array = Array[1, 'a', nil]
+    array[0].should == 1
+    array[1].should == 'a'
+    array[2].should == nil
+  end
+
+  it "when applied to a literal nested array, unpacks its elements into the containing array" do
+    Array[1, 2, *[3, 4, 5]].should == [1, 2, 3, 4, 5]
+  end
+
+  it "when applied to a nested referenced array, unpacks its elements into the containing array" do
+    splatted_array = Array[3, 4, 5]
+    Array[1, 2, *splatted_array].should == [1, 2, 3, 4, 5]
+  end
+
+  it "can unpack 2 or more nested referenced array" do
+    splatted_array = Array[3, 4, 5]
+    splatted_array2 = Array[6, 7, 8]
+    Array[1, 2, *splatted_array, *splatted_array2].should == [1, 2, 3, 4, 5, 6, 7, 8]
+  end
+
+  it "constructs a nested Hash for tailing key-value pairs" do
+    Array[1, 2, 3 => 4, 5 => 6].should == [1, 2, { 3 => 4, 5 => 6 }]
+  end
+
+  describe "with a subclass of Array" do
+    before :each do
+      ScratchPad.clear
+    end
+
+    it "returns an instance of the subclass" do
+      ArraySpecs::MyArray[1, 2, 3].should.instance_of?(ArraySpecs::MyArray)
+    end
+
+    it "does not call #initialize on the subclass instance" do
+      ArraySpecs::MyArray[1, 2, 3].should == [1, 2, 3]
+      ScratchPad.recorded.should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/array/element_set_spec.rb b/spec/ruby/core/array/element_set_spec.rb
new file mode 100644
index 0000000000..671e4338de
--- /dev/null
+++ b/spec/ruby/core/array/element_set_spec.rb
@@ -0,0 +1,537 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#[]=" do
+  it "sets the value of the element at index" do
+    a = [1, 2, 3, 4]
+    a[2] = 5
+    a[-1] = 6
+    a[5] = 3
+    a.should == [1, 2, 5, 6, nil, 3]
+
+    a = []
+    a[4] = "e"
+    a.should == [nil, nil, nil, nil, "e"]
+    a[3] = "d"
+    a.should == [nil, nil, nil, "d", "e"]
+    a[0] = "a"
+    a.should == ["a", nil, nil, "d", "e"]
+    a[-3] = "C"
+    a.should == ["a", nil, "C", "d", "e"]
+    a[-1] = "E"
+    a.should == ["a", nil, "C", "d", "E"]
+    a[-5] = "A"
+    a.should == ["A", nil, "C", "d", "E"]
+    a[5] = "f"
+    a.should == ["A", nil, "C", "d", "E", "f"]
+    a[1] = []
+    a.should == ["A", [], "C", "d", "E", "f"]
+    a[-1] = nil
+    a.should == ["A", [], "C", "d", "E", nil]
+  end
+
+  it "sets the section defined by [start,length] to other" do
+    a = [1, 2, 3, 4, 5, 6]
+    a[0, 1] = 2
+    a[3, 2] = ['a', 'b', 'c', 'd']
+    a.should == [2, 2, 3, "a", "b", "c", "d", 6]
+  end
+
+  it "replaces the section defined by [start,length] with the given values" do
+    a = [1, 2, 3, 4, 5, 6]
+    a[3, 2] = 'a', 'b', 'c', 'd'
+    a.should == [1, 2, 3, "a", "b", "c", "d", 6]
+  end
+
+  it "just sets the section defined by [start,length] to other even if other is nil" do
+    a = ['a', 'b', 'c', 'd', 'e']
+    a[1, 3] = nil
+    a.should == ["a", nil, "e"]
+  end
+
+  it "returns nil if the rhs is nil" do
+    a = [1, 2, 3]
+    (a[1, 3] = nil).should == nil
+    (a[1..3] = nil).should == nil
+  end
+
+  it "sets the section defined by range to other" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[1...2] = 9
+    a[3..6] = [6, 6, 6]
+    a.should == [6, 9, 4, 6, 6, 6]
+  end
+
+  it "replaces the section defined by range with the given values" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[3..6] = :a, :b, :c
+    a.should == [6, 5, 4, :a, :b, :c]
+  end
+
+  it "just sets the section defined by range to other even if other is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[0..1] = nil
+    a.should == [nil, 3, 4, 5]
+  end
+
+  it 'expands and nil-pads the array if section assigned by range is outside array boundaries' do
+    a = ['a']
+    a[3..4] = ['b', 'c']
+    a.should == ['a', nil, nil, 'b', 'c']
+  end
+
+  it "calls to_int on its start and length arguments" do
+    obj = mock('to_int')
+    obj.stub!(:to_int).and_return(2)
+
+    a = [1, 2, 3, 4]
+    a[obj, 0] = [9]
+    a.should == [1, 2, 9, 3, 4]
+    a[obj, obj] = []
+    a.should == [1, 2, 4]
+    a[obj] = -1
+    a.should == [1, 2, -1]
+  end
+
+  it "checks frozen before attempting to coerce arguments" do
+    a = [1,2,3,4].freeze
+    -> {a[:foo] = 1}.should.raise(FrozenError)
+    -> {a[:foo, :bar] = 1}.should.raise(FrozenError)
+  end
+
+  it "sets elements in the range arguments when passed ranges" do
+    ary = [1, 2, 3]
+    rhs = [nil, [], ["x"], ["x", "y"]]
+    (0 .. ary.size + 2).each do |a|
+      (a .. ary.size + 3).each do |b|
+        rhs.each do |c|
+          ary1 = ary.dup
+          ary1[a .. b] = c
+          ary2 = ary.dup
+          ary2[a, 1 + b-a] = c
+          ary1.should == ary2
+
+          ary1 = ary.dup
+          ary1[a ... b] = c
+          ary2 = ary.dup
+          ary2[a, b-a] = c
+          ary1.should == ary2
+        end
+      end
+    end
+  end
+
+  it "inserts the given elements with [range] which the range is zero-width" do
+    ary = [1, 2, 3]
+    ary[1...1] = 0
+    ary.should == [1, 0, 2, 3]
+    ary[1...1] = [5]
+    ary.should == [1, 5, 0, 2, 3]
+    ary[1...1] = :a, :b, :c
+    ary.should == [1, :a, :b, :c, 5, 0, 2, 3]
+  end
+
+  it "inserts the given elements with [start, length] which length is zero" do
+    ary = [1, 2, 3]
+    ary[1, 0] = 0
+    ary.should == [1, 0, 2, 3]
+    ary[1, 0] = [5]
+    ary.should == [1, 5, 0, 2, 3]
+    ary[1, 0] = :a, :b, :c
+    ary.should == [1, :a, :b, :c, 5, 0, 2, 3]
+  end
+
+  # Now we only have to test cases where the start, length interface would
+  # have raise an exception because of negative size
+  it "inserts the given elements with [range] which the range has negative width" do
+    ary = [1, 2, 3]
+    ary[1..0] = 0
+    ary.should == [1, 0, 2, 3]
+    ary[1..0] = [4, 3]
+    ary.should == [1, 4, 3, 0, 2, 3]
+    ary[1..0] = :a, :b, :c
+    ary.should == [1, :a, :b, :c, 4, 3, 0, 2, 3]
+  end
+
+  it "just inserts nil if the section defined by range is zero-width and the rhs is nil" do
+    ary = [1, 2, 3]
+    ary[1...1] = nil
+    ary.should == [1, nil, 2, 3]
+  end
+
+  it "just inserts nil if the section defined by range has negative width and the rhs is nil" do
+    ary = [1, 2, 3]
+    ary[1..0] = nil
+    ary.should == [1, nil, 2, 3]
+  end
+
+  it "does nothing if the section defined by range is zero-width and the rhs is an empty array" do
+    ary = [1, 2, 3]
+    ary[1...1] = []
+    ary.should == [1, 2, 3]
+  end
+
+  it "does nothing if the section defined by range has negative width and the rhs is an empty array" do
+    ary = [1, 2, 3, 4, 5]
+    ary[1...0] = []
+    ary.should == [1, 2, 3, 4, 5]
+    ary[-2..2] = []
+    ary.should == [1, 2, 3, 4, 5]
+  end
+
+  it "tries to convert Range elements to Integers using #to_int with [m..n] and [m...n]" do
+    from = mock('from')
+    to = mock('to')
+
+    # So we can construct a range out of them...
+    def from.<=>(o) 0 end
+    def to.<=>(o) 0 end
+
+    def from.to_int() 1 end
+    def to.to_int() -2 end
+
+    a = [1, 2, 3, 4]
+
+    a[from .. to] = ["a", "b", "c"]
+    a.should == [1, "a", "b", "c", 4]
+
+    a[to .. from] = ["x"]
+    a.should == [1, "a", "b", "x", "c", 4]
+    -> { a["a" .. "b"] = []  }.should.raise(TypeError)
+    -> { a[from .. "b"] = [] }.should.raise(TypeError)
+  end
+
+  it "raises an IndexError when passed indexes out of bounds" do
+    a = [1, 2, 3, 4]
+    -> { a[-5] = ""      }.should.raise(IndexError)
+    -> { a[-5, -1] = ""  }.should.raise(IndexError)
+    -> { a[-5, 0] = ""   }.should.raise(IndexError)
+    -> { a[-5, 1] = ""   }.should.raise(IndexError)
+    -> { a[-5, 2] = ""   }.should.raise(IndexError)
+    -> { a[-5, 10] = ""  }.should.raise(IndexError)
+
+    -> { a[-5..-5] = ""  }.should.raise(RangeError)
+    -> { a[-5...-5] = "" }.should.raise(RangeError)
+    -> { a[-5..-4] = ""  }.should.raise(RangeError)
+    -> { a[-5...-4] = "" }.should.raise(RangeError)
+    -> { a[-5..10] = ""  }.should.raise(RangeError)
+    -> { a[-5...10] = "" }.should.raise(RangeError)
+
+    # ok
+    a[0..-9] = [1]
+    a.should == [1, 1, 2, 3, 4]
+  end
+
+  it "calls to_ary on its rhs argument for multi-element sets" do
+    obj = mock('to_ary')
+    def obj.to_ary() [1, 2, 3] end
+    ary = [1, 2]
+    ary[0, 0] = obj
+    ary.should == [1, 2, 3, 1, 2]
+    ary[1, 10] = obj
+    ary.should == [1, 1, 2, 3]
+  end
+
+  it "does not call to_ary on rhs array subclasses for multi-element sets" do
+    ary = []
+    ary[0, 0] = ArraySpecs::ToAryArray[5, 6, 7]
+    ary.should == [5, 6, 7]
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array[0, 0] = [] }.should.raise(FrozenError)
+  end
+end
+
+describe "Array#[]= with [index]" do
+  it "returns value assigned if idx is inside array" do
+    a = [1, 2, 3, 4, 5]
+    (a[3] = 6).should == 6
+  end
+
+  it "returns value assigned if idx is right beyond right array boundary" do
+    a = [1, 2, 3, 4, 5]
+    (a[5] = 6).should == 6
+  end
+
+  it "returns value assigned if idx far beyond right array boundary" do
+    a = [1, 2, 3, 4, 5]
+    (a[10] = 6).should == 6
+  end
+
+  it "sets the value of the element at index" do
+    a = [1, 2, 3, 4]
+    a[2] = 5
+    a[-1] = 6
+    a[5] = 3
+    a.should == [1, 2, 5, 6, nil, 3]
+  end
+
+  it "sets the value of the element if it is right beyond the array boundary" do
+    a = [1, 2, 3, 4]
+    a[4] = 8
+    a.should == [1, 2, 3, 4, 8]
+  end
+
+end
+
+describe "Array#[]= with [index, count]" do
+  it "returns non-array value if non-array value assigned" do
+    a = [1, 2, 3, 4, 5]
+    (a[2, 3] = 10).should == 10
+  end
+
+  it "returns array if array assigned" do
+    a = [1, 2, 3, 4, 5]
+    (a[2, 3] = [4, 5]).should == [4, 5]
+  end
+
+  it "accepts a frozen String literal as RHS" do
+    a = ['a', 'b', 'c']
+    a[0, 2] = 'd'.freeze
+    a.should == ['d', 'c']
+  end
+
+  it "just sets the section defined by [start,length] to nil even if the rhs is nil" do
+    a = ['a', 'b', 'c', 'd', 'e']
+    a[1, 3] = nil
+    a.should == ["a", nil, "e"]
+  end
+
+  it "just sets the section defined by [start,length] to nil if negative index within bounds, cnt > 0 and the rhs is nil" do
+    a = ['a', 'b', 'c', 'd', 'e']
+    a[-3, 2] = nil
+    a.should == ["a", "b", nil, "e"]
+  end
+
+  it "replaces the section defined by [start,length] to other" do
+    a = [1, 2, 3, 4, 5, 6]
+    a[0, 1] = 2
+    a[3, 2] = ['a', 'b', 'c', 'd']
+    a.should == [2, 2, 3, "a", "b", "c", "d", 6]
+  end
+
+  it "replaces the section to other if idx < 0 and cnt > 0" do
+    a = [1, 2, 3, 4, 5, 6]
+    a[-3, 2] = ["x", "y", "z"]
+    a.should == [1, 2, 3, "x", "y", "z", 6]
+  end
+
+  it "replaces the section to other even if cnt spanning beyond the array boundary" do
+    a = [1, 2, 3, 4, 5]
+    a[-1, 3] = [7, 8]
+    a.should == [1, 2, 3, 4, 7, 8]
+  end
+
+  it "pads the Array with nils if the span is past the end" do
+    a = [1, 2, 3, 4, 5]
+    a[10, 1] = [1]
+    a.should == [1, 2, 3, 4, 5, nil, nil, nil, nil, nil, 1]
+
+    b = [1, 2, 3, 4, 5]
+    b[10, 0] = [1]
+    a.should == [1, 2, 3, 4, 5, nil, nil, nil, nil, nil, 1]
+
+    c = [1, 2, 3, 4, 5]
+    c[10, 0] = []
+    c.should == [1, 2, 3, 4, 5, nil, nil, nil, nil, nil]
+  end
+
+  it "inserts other section in place defined by idx" do
+    a = [1, 2, 3, 4, 5]
+    a[3, 0] = [7, 8]
+    a.should == [1, 2, 3, 7, 8, 4, 5]
+
+    b = [1, 2, 3, 4, 5]
+    b[1, 0] = b
+    b.should == [1, 1, 2, 3, 4, 5, 2, 3, 4, 5]
+  end
+
+  it "raises an IndexError when passed start and negative length" do
+    a = [1, 2, 3, 4]
+    -> { a[-2, -1] = "" }.should.raise(IndexError)
+    -> { a[0, -1] = ""  }.should.raise(IndexError)
+    -> { a[2, -1] = ""  }.should.raise(IndexError)
+    -> { a[4, -1] = ""  }.should.raise(IndexError)
+    -> { a[10, -1] = "" }.should.raise(IndexError)
+    -> { [1, 2, 3, 4,  5][2, -1] = [7, 8] }.should.raise(IndexError)
+  end
+end
+
+describe "Array#[]= with [m..n]" do
+  it "returns non-array value if non-array value assigned" do
+    a = [1, 2, 3, 4, 5]
+    (a[2..4] = 10).should == 10
+    (a.[]=(2..4, 10)).should == 10
+  end
+
+  it "returns array if array assigned" do
+    a = [1, 2, 3, 4, 5]
+    (a[2..4] = [7, 8]).should == [7, 8]
+    (a.[]=(2..4, [7, 8])).should == [7, 8]
+  end
+
+  it "just sets the section defined by range to nil even if the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[0..1] = nil
+    a.should == [nil, 3, 4, 5]
+  end
+
+  it "just sets the section defined by range to nil if m and n < 0 and the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[-3..-2] = nil
+    a.should == [1, 2, nil, 5]
+  end
+
+  it "replaces the section defined by range" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[1...2] = 9
+    a[3..6] = [6, 6, 6]
+    a.should == [6, 9, 4, 6, 6, 6]
+  end
+
+  it "replaces the section if m and n < 0" do
+    a = [1, 2, 3, 4, 5]
+    a[-3..-2] = [7, 8, 9]
+    a.should == [1, 2, 7, 8, 9, 5]
+  end
+
+  it "replaces the section if m < 0 and n > 0" do
+    a = [1, 2, 3, 4, 5]
+    a[-4..3] = [8]
+    a.should == [1, 8, 5]
+  end
+
+  it "inserts the other section at m if m > n" do
+    a = [1, 2, 3, 4, 5]
+    a[3..1] = [8]
+    a.should == [1, 2, 3, 8, 4, 5]
+  end
+
+  it "inserts at the end if m > the array size" do
+    a = [1, 2, 3]
+    a[3..3] = [4]
+    a.should == [1, 2, 3, 4]
+    a[5..7] = [6]
+    a.should == [1, 2, 3, 4, nil, 6]
+  end
+
+  describe "Range subclasses" do
+    before :each do
+      @range_incl = ArraySpecs::MyRange.new(1, 2)
+      @range_excl = ArraySpecs::MyRange.new(-3, -1, true)
+    end
+
+    it "accepts Range subclasses" do
+      a = [1, 2, 3, 4]
+
+      a[@range_incl] = ["a", "b"]
+      a.should == [1, "a", "b", 4]
+      a[@range_excl] = ["A", "B"]
+      a.should == [1, "A", "B", 4]
+    end
+
+    it "returns non-array value if non-array value assigned" do
+      a = [1, 2, 3, 4, 5]
+      (a[@range_incl] = 10).should == 10
+      (a.[]=(@range_incl, 10)).should == 10
+    end
+
+    it "returns array if array assigned" do
+      a = [1, 2, 3, 4, 5]
+      (a[@range_incl] = [7, 8]).should == [7, 8]
+      a.[]=(@range_incl, [7, 8]).should == [7, 8]
+    end
+  end
+end
+
+describe "Array#[]= with [m..]" do
+  it "just sets the section defined by range to nil even if the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(2..)")] = nil
+    a.should == [1, 2, nil]
+  end
+
+  it "just sets the section defined by range to nil if m and n < 0 and the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(-3..)")] = nil
+    a.should == [1, 2, nil]
+  end
+
+  it "replaces the section defined by range" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[eval("(3...)")] = 9
+    a.should == [6, 5, 4, 9]
+    a[eval("(2..)")] = [7, 7, 7]
+    a.should == [6, 5, 7, 7, 7]
+  end
+
+  it "replaces the section if m and n < 0" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(-3..)")] = [7, 8, 9]
+    a.should == [1, 2, 7, 8, 9]
+  end
+
+  it "inserts at the end if m > the array size" do
+    a = [1, 2, 3]
+    a[eval("(3..)")] = [4]
+    a.should == [1, 2, 3, 4]
+    a[eval("(5..)")] = [6]
+    a.should == [1, 2, 3, 4, nil, 6]
+  end
+end
+
+describe "Array#[]= with [..n] and [...n]" do
+  it "just sets the section defined by range to nil even if the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[(..2)] = nil
+    a.should == [nil, 4, 5]
+    a[(...2)] = nil
+    a.should == [nil, 5]
+  end
+
+  it "just sets the section defined by range to nil if n < 0 and the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[(..-3)] = nil
+    a.should == [nil, 4, 5]
+    a[(...-1)] = [nil, 5]
+  end
+
+  it "replaces the section defined by range" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[(...3)] = 9
+    a.should == [9, 3, 2, 1]
+    a[(..2)] = [7, 7, 7, 7, 7]
+    a.should == [7, 7, 7, 7, 7, 1]
+  end
+
+  it "replaces the section if n < 0" do
+    a = [1, 2, 3, 4, 5]
+    a[(..-2)] = [7, 8, 9]
+    a.should == [7, 8, 9, 5]
+  end
+
+  it "replaces everything if n > the array size" do
+    a = [1, 2, 3]
+    a[(...7)] = [4]
+    a.should == [4]
+  end
+
+  it "inserts at the beginning if n < negative the array size" do
+    a = [1, 2, 3]
+    a[(..-7)] = [4]
+    a.should == [4, 1, 2, 3]
+    a[(...-10)] = [6]
+    a.should == [6, 4, 1, 2, 3]
+  end
+end
+
+describe "Array#[] after a shift" do
+  it "works for insertion" do
+    a = [1,2]
+    a.shift
+    a.shift
+    a[0,0] = [3,4]
+    a.should == [3,4]
+  end
+end
diff --git a/spec/ruby/core/array/empty_spec.rb b/spec/ruby/core/array/empty_spec.rb
new file mode 100644
index 0000000000..f70b1b6ebe
--- /dev/null
+++ b/spec/ruby/core/array/empty_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#empty?" do
+  it "returns true if the array has no elements" do
+    [].should.empty?
+    [1].should_not.empty?
+    [1, 2].should_not.empty?
+  end
+end
diff --git a/spec/ruby/core/array/eql_spec.rb b/spec/ruby/core/array/eql_spec.rb
new file mode 100644
index 0000000000..9a7447c2e8
--- /dev/null
+++ b/spec/ruby/core/array/eql_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/eql'
+
+describe "Array#eql?" do
+  it_behaves_like :array_eql, :eql?
+
+  it "returns false if any corresponding elements are not #eql?" do
+    [1, 2, 3, 4].should_not.eql?([1, 2, 3, 4.0])
+  end
+
+  it "returns false if other is not a kind of Array" do
+    obj = mock("array eql?")
+    obj.should_not_receive(:to_ary)
+    obj.should_not_receive(:eql?)
+
+    [1, 2, 3].should_not.eql?(obj)
+  end
+end
diff --git a/spec/ruby/core/array/equal_value_spec.rb b/spec/ruby/core/array/equal_value_spec.rb
new file mode 100644
index 0000000000..4f7c0ce5e3
--- /dev/null
+++ b/spec/ruby/core/array/equal_value_spec.rb
@@ -0,0 +1,51 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/eql'
+
+describe "Array#==" do
+  it_behaves_like :array_eql, :==
+
+  it "compares with an equivalent Array-like object using #to_ary" do
+    obj = mock('array-like')
+    obj.should_receive(:respond_to?).at_least(1).with(:to_ary).and_return(true)
+    obj.should_receive(:==).with([1]).at_least(1).and_return(true)
+
+    ([1] == obj).should == true
+    ([[1]] == [obj]).should == true
+    ([[[1], 3], 2] == [[obj, 3], 2]).should == true
+
+    # recursive arrays
+    arr1 = [[1]]
+    arr1 << arr1
+    arr2 = [obj]
+    arr2 << arr2
+    (arr1 == arr2).should == true
+    (arr2 == arr1).should == true
+  end
+
+  it "returns false if any corresponding elements are not #==" do
+    a = ["a", "b", "c"]
+    b = ["a", "b", "not equal value"]
+    a.should_not == b
+
+    c = mock("c")
+    c.should_receive(:==).and_return(false)
+    ["a", "b", c].should_not == a
+  end
+
+  it "returns true if corresponding elements are #==" do
+    [].should == []
+    ["a", "c", 7].should == ["a", "c", 7]
+
+    [1, 2, 3].should == [1.0, 2.0, 3.0]
+
+    obj = mock('5')
+    obj.should_receive(:==).and_return(true)
+    [obj].should == [5]
+  end
+
+  # See https://bugs.ruby-lang.org/issues/1720
+  it "returns true for [NaN] == [NaN] because Array#== first checks with #equal? and NaN.equal?(NaN) is true" do
+    [Float::NAN].should == [Float::NAN]
+  end
+end
diff --git a/spec/ruby/core/array/fetch_spec.rb b/spec/ruby/core/array/fetch_spec.rb
new file mode 100644
index 0000000000..ee94cfcbb2
--- /dev/null
+++ b/spec/ruby/core/array/fetch_spec.rb
@@ -0,0 +1,55 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#fetch" do
+  it "returns the element at the passed index" do
+    [1, 2, 3].fetch(1).should == 2
+    [nil].fetch(0).should == nil
+  end
+
+  it "counts negative indices backwards from end" do
+    [1, 2, 3, 4].fetch(-1).should == 4
+  end
+
+  it "raises an IndexError if there is no element at index" do
+    -> { [1, 2, 3].fetch(3) }.should.raise(IndexError, "index 3 outside of array bounds: -3...3")
+    -> { [1, 2, 3].fetch(-4) }.should.raise(IndexError, "index -4 outside of array bounds: -3...3")
+    -> { [].fetch(0) }.should.raise(IndexError, "index 0 outside of array bounds: 0...0")
+  end
+
+  it "returns default if there is no element at index if passed a default value" do
+    [1, 2, 3].fetch(5, :not_found).should == :not_found
+    [1, 2, 3].fetch(5, nil).should == nil
+    [1, 2, 3].fetch(-4, :not_found).should == :not_found
+    [nil].fetch(0, :not_found).should == nil
+  end
+
+  it "returns the value of block if there is no element at index if passed a block" do
+    [1, 2, 3].fetch(9) { |i| i * i }.should == 81
+    [1, 2, 3].fetch(-9) { |i| i * i }.should == 81
+  end
+
+  it "passes the original index argument object to the block, not the converted Integer" do
+    o = mock('5')
+    def o.to_int(); 5; end
+
+    [1, 2, 3].fetch(o) { |i| i }.should.equal?(o)
+  end
+
+  it "gives precedence to the default block over the default argument" do
+    -> {
+      @result = [1, 2, 3].fetch(9, :foo) { |i| i * i }
+    }.should complain(/block supersedes default value argument/)
+    @result.should == 81
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(2)
+    ["a", "b", "c"].fetch(obj).should == "c"
+  end
+
+  it "raises a TypeError when the passed argument can't be coerced to Integer" do
+    -> { [].fetch("cat") }.should.raise(TypeError, "no implicit conversion of String into Integer")
+  end
+end
diff --git a/spec/ruby/core/array/fetch_values_spec.rb b/spec/ruby/core/array/fetch_values_spec.rb
new file mode 100644
index 0000000000..237d6ad7f7
--- /dev/null
+++ b/spec/ruby/core/array/fetch_values_spec.rb
@@ -0,0 +1,55 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#fetch_values" do
+  before :each do
+    @array = [:a, :b, :c]
+  end
+
+  ruby_version_is "3.4" do
+    describe "with matched indexes" do
+      it "returns the values for indexes" do
+        @array.fetch_values(0).should == [:a]
+        @array.fetch_values(0, 2).should == [:a, :c]
+        @array.fetch_values(-1).should == [:c]
+      end
+
+      it "returns the values for indexes ordered in the order of the requested indexes" do
+        @array.fetch_values(2, 0).should == [:c, :a]
+      end
+    end
+
+    describe "with unmatched indexes" do
+      it "raises a index error if no block is provided" do
+        -> { @array.fetch_values(0, 1, 44) }.should.raise(IndexError, "index 44 outside of array bounds: -3...3")
+      end
+
+      it "returns the default value from block" do
+        @array.fetch_values(44) { |index| "`#{index}' is not found" }.should == ["`44' is not found"]
+        @array.fetch_values(0, 44) { |index| "`#{index}' is not found" }.should == [:a, "`44' is not found"]
+      end
+    end
+
+    describe "without keys" do
+      it "returns an empty Array" do
+        @array.fetch_values.should == []
+      end
+    end
+
+    it "tries to convert the passed argument to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(2)
+      @array.fetch_values(obj).should == [:c]
+    end
+
+    it "does not support a Range object as argument" do
+      -> {
+        @array.fetch_values(1..2)
+      }.should.raise(TypeError, "no implicit conversion of Range into Integer")
+    end
+
+    it "raises a TypeError when the passed argument can't be coerced to Integer" do
+      -> { [].fetch_values("cat") }.should.raise(TypeError, "no implicit conversion of String into Integer")
+    end
+  end
+end
diff --git a/spec/ruby/core/array/fill_spec.rb b/spec/ruby/core/array/fill_spec.rb
new file mode 100644
index 0000000000..e4d51bd998
--- /dev/null
+++ b/spec/ruby/core/array/fill_spec.rb
@@ -0,0 +1,374 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#fill" do
+  before :all do
+    @never_passed = -> i do
+      raise ExpectationNotMetError, "the control path should not pass here"
+    end
+  end
+
+  it "returns self" do
+    ary = [1, 2, 3]
+    ary.fill(:a).should.equal?(ary)
+  end
+
+  it "is destructive" do
+    ary = [1, 2, 3]
+    ary.fill(:a)
+    ary.should == [:a, :a, :a]
+  end
+
+  it "does not replicate the filler" do
+    ary = [1, 2, 3, 4]
+    str = +"x"
+    ary.fill(str).should == [str, str, str, str]
+    str << "y"
+    ary.should == [str, str, str, str]
+    ary[0].should.equal?(str)
+    ary[1].should.equal?(str)
+    ary[2].should.equal?(str)
+    ary[3].should.equal?(str)
+  end
+
+  it "replaces all elements in the array with the filler if not given a index nor a length" do
+    ary = ['a', 'b', 'c', 'duh']
+    ary.fill(8).should == [8, 8, 8, 8]
+
+    str = "x"
+    ary.fill(str).should == [str, str, str, str]
+  end
+
+  it "replaces all elements with the value of block (index given to block)" do
+    [nil, nil, nil, nil].fill { |i| i * 2 }.should == [0, 2, 4, 6]
+  end
+
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.fill('x') }.should.raise(FrozenError)
+  end
+
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.fill('x') }.should.raise(FrozenError)
+  end
+
+  it "raises an ArgumentError if 4 or more arguments are passed when no block given" do
+    [].fill('a').should == []
+    [].fill('a', 1).should == []
+    [].fill('a', 1, 2).should == [nil, 'a', 'a']
+    -> { [].fill('a', 1, 2, true) }.should.raise(ArgumentError)
+  end
+
+  it "raises an ArgumentError if no argument passed and no block given" do
+    -> { [].fill }.should.raise(ArgumentError)
+  end
+
+  it "raises an ArgumentError if 3 or more arguments are passed when a block given" do
+    [].fill() {|i|}.should == []
+    [].fill(1) {|i|}.should == []
+    [].fill(1, 2) {|i|}.should == [nil, nil, nil]
+    -> { [].fill(1, 2, true) {|i|} }.should.raise(ArgumentError)
+  end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.fill { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "only changes elements before error is raised, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.fill do |i|
+        case i
+        when 0 then -1
+        when 1 then -2
+        when 2 then raise StandardError, 'Oops'
+        else 0
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [-1, -2, 3, 4]
+  end
+
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.fill do |index|
+      ScratchPad << index
+      array << i if i < 100
+      i++
+      index
+    end
+
+    ScratchPad.recorded.should == [0, 1, 2]
+  end
+end
+
+describe "Array#fill with (filler, index, length)" do
+  it "replaces length elements beginning with the index with the filler if given an index and a length" do
+    ary = [1, 2, 3, 4, 5, 6]
+    ary.fill('x', 2, 3).should == [1, 2, 'x', 'x', 'x', 6]
+  end
+
+  it "replaces length elements beginning with the index with the value of block" do
+    [true, false, true, false, true, false, true].fill(1, 4) { |i| i + 3 }.should == [true, 4, 5, 6, 7, false, true]
+  end
+
+  it "replaces all elements after the index if given an index and no length" do
+    ary = [1, 2, 3]
+    ary.fill('x', 1).should == [1, 'x', 'x']
+    ary.fill(1){|i| i*2}.should == [1, 2, 4]
+  end
+
+  it "replaces all elements after the index if given an index and nil as a length" do
+    a = [1, 2, 3]
+    a.fill('x', 1, nil).should == [1, 'x', 'x']
+    a.fill(1, nil){|i| i*2}.should == [1, 2, 4]
+    a.fill('y', nil).should == ['y', 'y', 'y']
+  end
+
+  it "replaces the last (-n) elements if given an index n which is negative and no length" do
+    a = [1, 2, 3, 4, 5]
+    a.fill('x', -2).should == [1, 2, 3, 'x', 'x']
+    a.fill(-2){|i| i.to_s}.should == [1, 2, 3, '3', '4']
+  end
+
+  it "replaces the last (-n) elements if given an index n which is negative and nil as a length" do
+    a = [1, 2, 3, 4, 5]
+    a.fill('x', -2, nil).should == [1, 2, 3, 'x', 'x']
+    a.fill(-2, nil){|i| i.to_s}.should == [1, 2, 3, '3', '4']
+  end
+
+  it "makes no modifications if given an index greater than end and no length" do
+    [1, 2, 3, 4, 5].fill('a', 5).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill(5, &@never_passed).should == [1, 2, 3, 4, 5]
+  end
+
+  it "makes no modifications if given an index greater than end and nil as a length" do
+    [1, 2, 3, 4, 5].fill('a', 5, nil).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill(5, nil, &@never_passed).should == [1, 2, 3, 4, 5]
+  end
+
+  it "replaces length elements beginning with start index if given an index >= 0 and a length >= 0" do
+    [1, 2, 3, 4, 5].fill('a', 2, 0).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill('a', 2, 2).should == [1, 2, "a", "a", 5]
+
+    [1, 2, 3, 4, 5].fill(2, 0, &@never_passed).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill(2, 2){|i| i*2}.should == [1, 2, 4, 6, 5]
+  end
+
+  it "increases the Array size when necessary" do
+    a = [1, 2, 3]
+    a.size.should == 3
+    a.fill 'a', 0, 10
+    a.size.should == 10
+  end
+
+  it "pads between the last element and the index with nil if given an index which is greater than size of the array" do
+    [1, 2, 3, 4, 5].fill('a', 8, 5).should == [1, 2, 3, 4, 5, nil, nil, nil, 'a', 'a', 'a', 'a', 'a']
+    [1, 2, 3, 4, 5].fill(8, 5){|i| 'a'}.should == [1, 2, 3, 4, 5, nil, nil, nil, 'a', 'a', 'a', 'a', 'a']
+  end
+
+  it "replaces length elements beginning with the (-n)th if given an index n < 0 and a length > 0" do
+    [1, 2, 3, 4, 5].fill('a', -2, 2).should == [1, 2, 3, "a", "a"]
+    [1, 2, 3, 4, 5].fill('a', -2, 4).should == [1, 2, 3, "a", "a", "a", "a"]
+
+    [1, 2, 3, 4, 5].fill(-2, 2){|i| 'a'}.should == [1, 2, 3, "a", "a"]
+    [1, 2, 3, 4, 5].fill(-2, 4){|i| 'a'}.should == [1, 2, 3, "a", "a", "a", "a"]
+  end
+
+  it "starts at 0 if the negative index is before the start of the array" do
+    [1, 2, 3, 4, 5].fill('a', -25, 3).should == ['a', 'a', 'a', 4, 5]
+    [1, 2, 3, 4, 5].fill('a', -10, 10).should == %w|a a a a a a a a a a|
+
+    [1, 2, 3, 4, 5].fill(-25, 3){|i| 'a'}.should == ['a', 'a', 'a', 4, 5]
+    [1, 2, 3, 4, 5].fill(-10, 10){|i| 'a'}.should == %w|a a a a a a a a a a|
+  end
+
+  it "makes no modifications if the given length <= 0" do
+    [1, 2, 3, 4, 5].fill('a', 2, 0).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill('a', -2, 0).should == [1, 2, 3, 4, 5]
+
+    [1, 2, 3, 4, 5].fill('a', 2, -2).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill('a', -2, -2).should == [1, 2, 3, 4, 5]
+
+    [1, 2, 3, 4, 5].fill(2, 0, &@never_passed).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill(-2, 0, &@never_passed).should == [1, 2, 3, 4, 5]
+
+    [1, 2, 3, 4, 5].fill(2, -2, &@never_passed).should == [1, 2, 3, 4, 5]
+    [1, 2, 3, 4, 5].fill(-2, -2, &@never_passed).should == [1, 2, 3, 4, 5]
+  end
+
+  # See: https://blade.ruby-lang.org/ruby-core/17481
+  it "does not raise an exception if the given length is negative and its absolute value does not exceed the index" do
+    [1, 2, 3, 4].fill('a', 3, -1).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -2).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -3).should == [1, 2, 3, 4]
+
+    [1, 2, 3, 4].fill(3, -1, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -2, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -3, &@never_passed).should == [1, 2, 3, 4]
+  end
+
+  it "does not raise an exception even if the given length is negative and its absolute value exceeds the index" do
+    [1, 2, 3, 4].fill('a', 3, -4).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -5).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -10000).should == [1, 2, 3, 4]
+
+    [1, 2, 3, 4].fill(3, -4, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -5, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -10000, &@never_passed).should == [1, 2, 3, 4]
+  end
+
+  it "tries to convert the second and third arguments to Integers using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(2, 2)
+    filler = mock('filler')
+    filler.should_not_receive(:to_int)
+    [1, 2, 3, 4, 5].fill(filler, obj, obj).should == [1, 2, filler, filler, 5]
+  end
+
+  it "raises a TypeError if the index is not numeric" do
+    -> { [].fill 'a', true }.should.raise(TypeError)
+
+    obj = mock('nonnumeric')
+    -> { [].fill('a', obj) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError when the length is not numeric" do
+    -> { [1, 2, 3].fill("x", 1, "foo") }.should.raise(TypeError, /no implicit conversion of String into Integer/)
+    -> { [1, 2, 3].fill("x", 1, :"foo") }.should.raise(TypeError, /no implicit conversion of Symbol into Integer/)
+    -> { [1, 2, 3].fill("x", 1, Object.new) }.should.raise(TypeError, /no implicit conversion of Object into Integer/)
+  end
+
+  not_supported_on :opal do
+    it "raises an ArgumentError or RangeError for too-large sizes" do
+      error_types = [RangeError, ArgumentError]
+      arr = [1, 2, 3]
+      -> { arr.fill(10, 1, fixnum_max) }.should.raise { |err| error_types.should.include?(err.class) }
+      -> { arr.fill(10, 1, bignum_value) }.should.raise(RangeError)
+    end
+  end
+end
+
+describe "Array#fill with (filler, range)" do
+  it "replaces elements in range with object" do
+    [1, 2, 3, 4, 5, 6].fill(8, 0..3).should == [8, 8, 8, 8, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(8, 0...3).should == [8, 8, 8, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 4..6).should == [1, 2, 3, 4, 'x', 'x', 'x']
+    [1, 2, 3, 4, 5, 6].fill('x', 4...6).should == [1, 2, 3, 4, 'x', 'x']
+    [1, 2, 3, 4, 5, 6].fill('x', -2..-1).should == [1, 2, 3, 4, 'x', 'x']
+    [1, 2, 3, 4, 5, 6].fill('x', -2...-1).should == [1, 2, 3, 4, 'x', 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -2...-2).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -2..-2).should == [1, 2, 3, 4, 'x', 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -2..0).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 0...0).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 1..1).should == [1, 'x', 3, 4, 5, 6]
+  end
+
+  it "replaces all elements in range with the value of block" do
+    [1, 1, 1, 1, 1, 1].fill(1..6) { |i| i + 1 }.should == [1, 2, 3, 4, 5, 6, 7]
+  end
+
+  it "increases the Array size when necessary" do
+    [1, 2, 3].fill('x', 1..6).should == [1, 'x', 'x', 'x', 'x', 'x', 'x']
+    [1, 2, 3].fill(1..6){|i| i+1}.should == [1, 2, 3, 4, 5, 6, 7]
+  end
+
+  it "raises a TypeError with range and length argument" do
+    -> { [].fill('x', 0 .. 2, 5) }.should.raise(TypeError)
+  end
+
+  it "replaces elements between the (-m)th to the last and the (n+1)th from the first if given an range m..n where m < 0 and n >= 0" do
+    [1, 2, 3, 4, 5, 6].fill('x', -4..4).should == [1, 2, 'x', 'x', 'x', 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -4...4).should == [1, 2, 'x', 'x', 5, 6]
+
+    [1, 2, 3, 4, 5, 6].fill(-4..4){|i| (i+1).to_s}.should == [1, 2, '3', '4', '5', 6]
+    [1, 2, 3, 4, 5, 6].fill(-4...4){|i| (i+1).to_s}.should == [1, 2, '3', '4', 5, 6]
+  end
+
+  it "replaces elements between the (-m)th and (-n)th to the last if given an range m..n where m < 0 and n < 0" do
+    [1, 2, 3, 4, 5, 6].fill('x', -4..-2).should == [1, 2, 'x', 'x', 'x', 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -4...-2).should == [1, 2, 'x', 'x', 5, 6]
+
+    [1, 2, 3, 4, 5, 6].fill(-4..-2){|i| (i+1).to_s}.should == [1, 2, '3', '4', '5', 6]
+    [1, 2, 3, 4, 5, 6].fill(-4...-2){|i| (i+1).to_s}.should == [1, 2, '3', '4', 5, 6]
+  end
+
+  it "replaces elements between the (m+1)th from the first and (-n)th to the last if given an range m..n where m >= 0 and n < 0" do
+    [1, 2, 3, 4, 5, 6].fill('x', 2..-2).should == [1, 2, 'x', 'x', 'x', 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 2...-2).should == [1, 2, 'x', 'x', 5, 6]
+
+    [1, 2, 3, 4, 5, 6].fill(2..-2){|i| (i+1).to_s}.should == [1, 2, '3', '4', '5', 6]
+    [1, 2, 3, 4, 5, 6].fill(2...-2){|i| (i+1).to_s}.should == [1, 2, '3', '4', 5, 6]
+  end
+
+  it "makes no modifications if given an range which implies a section of zero width" do
+    [1, 2, 3, 4, 5, 6].fill('x', 2...2).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -4...2).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -4...-4).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 2...-4).should == [1, 2, 3, 4, 5, 6]
+
+    [1, 2, 3, 4, 5, 6].fill(2...2, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(-4...2, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(-4...-4, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(2...-4, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+  end
+
+  it "makes no modifications if given an range which implies a section of negative width" do
+    [1, 2, 3, 4, 5, 6].fill('x', 2..1).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -4..1).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', -2..-4).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill('x', 2..-5).should == [1, 2, 3, 4, 5, 6]
+
+    [1, 2, 3, 4, 5, 6].fill(2..1, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(-4..1, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(-2..-4, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+    [1, 2, 3, 4, 5, 6].fill(2..-5, &@never_passed).should == [1, 2, 3, 4, 5, 6]
+  end
+
+  it "raises an exception if some of the given range lies before the first of the array" do
+    -> { [1, 2, 3].fill('x', -5..-3) }.should.raise(RangeError)
+    -> { [1, 2, 3].fill('x', -5...-3) }.should.raise(RangeError)
+    -> { [1, 2, 3].fill('x', -5..-4) }.should.raise(RangeError)
+
+    -> { [1, 2, 3].fill(-5..-3, &@never_passed) }.should.raise(RangeError)
+    -> { [1, 2, 3].fill(-5...-3, &@never_passed) }.should.raise(RangeError)
+    -> { [1, 2, 3].fill(-5..-4, &@never_passed) }.should.raise(RangeError)
+  end
+
+  it "tries to convert the start and end of the passed range to Integers using #to_int" do
+    obj = mock('to_int')
+    def obj.<=>(rhs); rhs == self ? 0 : nil end
+    obj.should_receive(:to_int).twice.and_return(2)
+    filler = mock('filler')
+    filler.should_not_receive(:to_int)
+    [1, 2, 3, 4, 5].fill(filler, obj..obj).should == [1, 2, filler, 4, 5]
+  end
+
+  it "raises a TypeError if the start or end of the passed range is not numeric" do
+    obj = mock('nonnumeric')
+    def obj.<=>(rhs); rhs == self ? 0 : nil end
+    -> { [].fill('a', obj..obj) }.should.raise(TypeError)
+  end
+
+  it "works with endless ranges" do
+    [1, 2, 3, 4].fill('x', eval("(1..)")).should == [1, 'x', 'x', 'x']
+    [1, 2, 3, 4].fill('x', eval("(3...)")).should == [1, 2, 3, 'x']
+    [1, 2, 3, 4].fill(eval("(1..)")) { |x| x + 2 }.should == [1, 3, 4, 5]
+    [1, 2, 3, 4].fill(eval("(3...)")) { |x| x + 2 }.should == [1, 2, 3, 5]
+  end
+
+  it "works with beginless ranges" do
+    [1, 2, 3, 4].fill('x', (..2)).should == ["x", "x", "x", 4]
+    [1, 2, 3, 4].fill((...2)) { |x| x + 2 }.should == [2, 3, 3, 4]
+  end
+end
diff --git a/spec/ruby/core/array/filter_spec.rb b/spec/ruby/core/array/filter_spec.rb
new file mode 100644
index 0000000000..6ebda61069
--- /dev/null
+++ b/spec/ruby/core/array/filter_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Array#filter" do
+  it "is an alias of Array#select" do
+    Array.instance_method(:filter).should == Array.instance_method(:select)
+  end
+end
+
+describe "Array#filter!" do
+  it "is an alias of Array#select!" do
+    Array.instance_method(:filter!).should == Array.instance_method(:select!)
+  end
+end
diff --git a/spec/ruby/core/array/find_index_spec.rb b/spec/ruby/core/array/find_index_spec.rb
new file mode 100644
index 0000000000..17ff6c04a7
--- /dev/null
+++ b/spec/ruby/core/array/find_index_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#find_index" do
+  it "returns the index of the first element == to object" do
+    x = mock('3')
+    def x.==(obj) 3 == obj; end
+
+    [2, x, 3, 1, 3, 1].find_index(3).should == 1
+    [2, 3.0, 3, x, 1, 3, 1].find_index(x).should == 1
+  end
+
+  it "returns 0 if first element == to object" do
+    [2, 1, 3, 2, 5].find_index(2).should == 0
+  end
+
+  it "returns size-1 if only last element == to object" do
+    [2, 1, 3, 1, 5].find_index(5).should == 4
+  end
+
+  it "returns nil if no element == to object" do
+    [2, 1, 1, 1, 1].find_index(3).should == nil
+  end
+
+  it "accepts a block instead of an argument" do
+    [4, 2, 1, 5, 1, 3].find_index {|x| x < 2}.should == 2
+  end
+
+  it "ignores the block if there is an argument" do
+    -> {
+      [4, 2, 1, 5, 1, 3].find_index(5) {|x| x < 2}.should == 3
+    }.should complain(/given block not used/)
+  end
+
+  describe "given no argument and no block" do
+    it "produces an Enumerator" do
+      [].find_index.should.instance_of?(Enumerator)
+    end
+  end
+
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :find_index
+end
diff --git a/spec/ruby/core/array/first_spec.rb b/spec/ruby/core/array/first_spec.rb
new file mode 100644
index 0000000000..2c343ac8f6
--- /dev/null
+++ b/spec/ruby/core/array/first_spec.rb
@@ -0,0 +1,93 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#first" do
+  it "returns the first element" do
+    %w{a b c}.first.should == 'a'
+    [nil].first.should == nil
+  end
+
+  it "returns nil if self is empty" do
+    [].first.should == nil
+  end
+
+  it "returns the first count elements if given a count" do
+    [true, false, true, nil, false].first(2).should == [true, false]
+  end
+
+  it "returns an empty array when passed count on an empty array" do
+    [].first(0).should == []
+    [].first(1).should == []
+    [].first(2).should == []
+  end
+
+  it "returns an empty array when passed count == 0" do
+    [1, 2, 3, 4, 5].first(0).should == []
+  end
+
+  it "returns an array containing the first element when passed count == 1" do
+    [1, 2, 3, 4, 5].first(1).should == [1]
+  end
+
+  it "raises an ArgumentError when count is negative" do
+    -> { [1, 2].first(-1) }.should.raise(ArgumentError)
+  end
+
+  it "raises a RangeError when count is a Bignum" do
+    -> { [].first(bignum_value) }.should.raise(RangeError)
+  end
+
+  it "returns the entire array when count > length" do
+    [1, 2, 3, 4, 5, 9].first(10).should == [1, 2, 3, 4, 5, 9]
+  end
+
+  it "returns an array which is independent to the original when passed count" do
+    ary = [1, 2, 3, 4, 5]
+    ary.first(0).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+    ary.first(1).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+    ary.first(6).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    empty.first.should.equal?(empty)
+
+    ary = ArraySpecs.head_recursive_array
+    ary.first.should.equal?(ary)
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(2)
+    [1, 2, 3, 4, 5].first(obj).should == [1, 2]
+  end
+
+  it "raises a TypeError if the passed argument is not numeric" do
+    -> { [1,2].first(nil) }.should.raise(TypeError)
+    -> { [1,2].first("a") }.should.raise(TypeError)
+
+    obj = mock("nonnumeric")
+    -> { [1,2].first(obj) }.should.raise(TypeError)
+  end
+
+  it "does not return subclass instance when passed count on Array subclasses" do
+    ArraySpecs::MyArray[].first(0).should.instance_of?(Array)
+    ArraySpecs::MyArray[].first(2).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].first(0).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].first(1).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].first(2).should.instance_of?(Array)
+  end
+
+  it "is not destructive" do
+    a = [1, 2, 3]
+    a.first
+    a.should == [1, 2, 3]
+    a.first(2)
+    a.should == [1, 2, 3]
+    a.first(3)
+    a.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/array/fixtures/classes.rb b/spec/ruby/core/array/fixtures/classes.rb
new file mode 100644
index 0000000000..05283c0f74
--- /dev/null
+++ b/spec/ruby/core/array/fixtures/classes.rb
@@ -0,0 +1,592 @@
+class Object
+  # This helper is defined here rather than in MSpec because
+  # it is only used in #pack specs.
+  def pack_format(count=nil, repeat=nil)
+    format = instance_variable_get(:@method)
+    format += count.to_s unless format == 'P' || format == 'p'
+    format *= repeat if repeat
+    format.dup # because it may then become tainted
+  end
+end
+
+module ArraySpecs
+  SampleRange = 0..1000
+  SampleCount = 1000
+
+  def self.frozen_array
+    [1,2,3].freeze
+  end
+
+  def self.empty_frozen_array
+    [].freeze
+  end
+
+  def self.recursive_array
+    a = [1, 'two', 3.0]
+    5.times { a << a }
+    a
+  end
+
+  def self.head_recursive_array
+    a =  []
+    5.times { a << a }
+    a << 1 << 'two' << 3.0
+    a
+  end
+
+  def self.empty_recursive_array
+    a = []
+    a << a
+    a
+  end
+
+  # Chi squared critical values for tests with n degrees of freedom at 99% confidence.
+  # Values obtained from NIST Engineering Statistic Handbook at
+  # https://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm
+
+  CHI_SQUARED_CRITICAL_VALUES = [
+    0,
+    6.635, 9.210, 11.345, 13.277, 15.086, 16.812, 18.475, 20.090, 21.666, 23.209,
+    24.725, 26.217, 27.688, 29.141, 30.578, 32.000, 33.409, 34.805, 36.191, 37.566,
+    38.932, 40.289, 41.638, 42.980, 44.314, 45.642, 46.963, 48.278, 49.588, 50.892,
+    52.191, 53.486, 54.776, 56.061, 57.342, 58.619, 59.893, 61.162, 62.428, 63.691,
+    64.950, 66.206, 67.459, 68.710, 69.957, 71.201, 72.443, 73.683, 74.919, 76.154,
+    77.386, 78.616, 79.843, 81.069, 82.292, 83.513, 84.733, 85.950, 87.166, 88.379,
+    89.591, 90.802, 92.010, 93.217, 94.422, 95.626, 96.828, 98.028, 99.228, 100.425,
+    101.621, 102.816, 104.010, 105.202, 106.393, 107.583, 108.771, 109.958, 111.144, 112.329,
+    113.512, 114.695, 115.876, 117.057, 118.236, 119.414, 120.591, 121.767, 122.942, 124.116,
+    125.289, 126.462, 127.633, 128.803, 129.973, 131.141, 132.309, 133.476, 134.642, 135.807,
+  ]
+
+  def self.measure_sample_fairness(size, samples, iters)
+    ary = Array.new(size) { |x| x }
+    expected = iters.fdiv size
+    (samples).times do |i|
+      chi_results = []
+      3.times do
+        counts = Array.new(size, 0)
+        iters.times do
+          x = ary.sample(samples)[i]
+          counts[x] += 1
+        end
+        chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
+        chi_results << chi_squared
+        break if chi_squared <= CHI_SQUARED_CRITICAL_VALUES[size]
+      end
+
+      chi_results.min.should <= CHI_SQUARED_CRITICAL_VALUES[size]
+    end
+  end
+
+  def self.measure_sample_fairness_large_sample_size(size, samples, iters)
+    ary = Array.new(size) { |x| x }
+    counts = Array.new(size, 0)
+    expected = (iters * samples).fdiv size
+    iters.times do
+      ary.sample(samples).each do |sample|
+        counts[sample] += 1
+      end
+    end
+    chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
+
+    # Chi squared critical values for tests with 4 degrees of freedom
+    # Values obtained from NIST Engineering Statistic Handbook at
+    # https://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm
+
+    chi_squared.should <= CHI_SQUARED_CRITICAL_VALUES[size]
+  end
+
+  class MyArray < Array
+    # The #initialize method has a different signature than Array to help
+    # catch places in the specs that do not assert the #initialize is not
+    # called when Array methods make new instances.
+    def initialize(a, b)
+      self << a << b
+      ScratchPad.record :my_array_initialize
+    end
+  end
+
+  class Sexp < Array
+    def initialize(*args)
+      super(args)
+    end
+  end
+
+  # TODO: replace specs that use this with #should_not_receive(:to_ary)
+  # expectations on regular objects (e.g. Array instances).
+  class ToAryArray < Array
+    def to_ary() ["to_ary", "was", "called!"] end
+  end
+
+  class MyRange < Range; end
+
+  class AssocKey
+    def ==(other); other == 'it'; end
+  end
+
+  class D
+    def <=>(obj)
+      return 4 <=> obj unless obj.class == D
+      0
+    end
+  end
+
+  class SubArray < Array
+    def initialize(*args)
+      ScratchPad.record args
+    end
+  end
+
+  class ArrayConvertible
+    attr_accessor :called
+    def initialize(*values, &block)
+      @values = values;
+    end
+
+    def to_a
+      self.called = :to_a
+      @values
+    end
+
+    def to_ary
+      self.called = :to_ary
+      @values
+    end
+  end
+
+  class ArrayMethodMissing
+    def initialize(*values, &block)
+      @values = values;
+    end
+
+    def method_missing(name, *args)
+      @values
+    end
+  end
+
+  class SortSame
+    def <=>(other); 0; end
+    def ==(other); true; end
+  end
+
+  class UFOSceptic
+    def <=>(other); raise "N-uh, UFO:s do not exist!"; end
+  end
+
+  class MockForCompared
+    @@count = 0
+    @@compared = false
+    def initialize
+      @@compared = false
+      @order = (@@count += 1)
+    end
+    def <=>(rhs)
+      @@compared = true
+      return rhs.order <=> self.order
+    end
+    def self.compared?
+      @@compared
+    end
+
+    protected
+    attr_accessor :order
+  end
+
+  class ComparableWithInteger
+    include Comparable
+    def initialize(num)
+      @num = num
+    end
+
+    def <=>(fixnum)
+      @num <=> fixnum
+    end
+  end
+
+  class Uncomparable
+    def <=>(obj)
+      nil
+    end
+  end
+
+  def self.universal_pack_object
+    obj = mock("string float int".freeze)
+    obj.stub!(:to_int).and_return(1)
+    obj.stub!(:to_str).and_return("1")
+    obj.stub!(:to_f).and_return(1.0)
+    obj
+  end
+
+  LargeArray = [
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_add_table",
+    "assert_difference",
+    "assert_operator",
+    "instance_variables",
+    "class",
+    "instance_variable_get",
+    "__class__",
+    "expects",
+    "assert_no_difference",
+    "name",
+    "assert_blank",
+    "assert_not_same",
+    "is_a?",
+    "test_add_table_with_decimals",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "assert_present",
+    "assert_no_match",
+    "__instance_of__",
+    "assert_deprecated",
+    "assert",
+    "assert_throws",
+    "kind_of?",
+    "try",
+    "__instance_variable_get__",
+    "object_id",
+    "timeout",
+    "instance_variable_set",
+    "assert_nothing_thrown",
+    "__instance_variable_set__",
+    "copy_object",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "assert_not_deprecated",
+    "assert_in_delta",
+    "id",
+    "copy_metaclass",
+    "test_create_table_without_a_block",
+    "dup",
+    "assert_not_nil",
+    "send",
+    "__instance_variables__",
+    "to_sql",
+    "mock",
+    "assert_send",
+    "instance_variable_defined?",
+    "clone",
+    "require",
+    "test_migrator",
+    "__instance_variable_defined_eh__",
+    "frozen?",
+    "test_add_column_not_null_with_default",
+    "freeze",
+    "test_migrator_one_up",
+    "test_migrator_one_down",
+    "singleton_methods",
+    "method_exists?",
+    "create_fixtures",
+    "test_migrator_one_up_one_down",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "instance_exec",
+    "__is_a__",
+    "test_migrator_double_up",
+    "stub",
+    "private_methods",
+    "stubs",
+    "test_migrator_double_down",
+    "fixture_path",
+    "private_singleton_methods",
+    "stub_everything",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "sequence",
+    "protected_methods",
+    "enum_for",
+    "test_finds_migrations",
+    "run_before_mocha",
+    "states",
+    "protected_singleton_methods",
+    "to_json",
+    "instance_values",
+    "==",
+    "mocha_setup",
+    "public_methods",
+    "test_finds_pending_migrations",
+    "mocha_verify",
+    "assert_kind_of",
+    "===",
+    "=~",
+    "test_relative_migrations",
+    "mocha_teardown",
+    "gem",
+    "mocha",
+    "test_only_loads_pending_migrations",
+    "test_add_column_with_precision_and_scale",
+    "require_or_load",
+    "eql?",
+    "require_dependency",
+    "test_native_types",
+    "test_target_version_zero_should_run_only_once",
+    "extend",
+    "to_matcher",
+    "unloadable",
+    "require_association",
+    "hash",
+    "__id__",
+    "load_dependency",
+    "equals",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_verbosity",
+    "kind_of",
+    "to_yaml",
+    "to_bool",
+    "test_migrator_verbosity_off",
+    "taint",
+    "test_migrator_going_down_due_to_version_target",
+    "tainted?",
+    "mocha_inspect",
+    "test_migrator_rollback",
+    "vim",
+    "untaint",
+    "taguri=",
+    "test_migrator_forward",
+    "test_schema_migrations_table_name",
+    "test_proper_table_name",
+    "all_of",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "_setup_callbacks",
+    "setup",
+    "Not",
+    "test_create_table_with_binary_column",
+    "assert_not_equal",
+    "enable_warnings",
+    "acts_like?",
+    "Rational",
+    "_removed_setup_callbacks",
+    "Table",
+    "bind",
+    "any_of",
+    "__method__",
+    "test_migrator_with_duplicates",
+    "_teardown_callbacks",
+    "method",
+    "test_migrator_with_duplicate_names",
+    "_removed_teardown_callbacks",
+    "any_parameters",
+    "test_migrator_with_missing_version_numbers",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_create_table_with_custom_sequence_name",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "_one_time_conditions_valid_14?",
+    "_one_time_conditions_valid_16?",
+    "run_callbacks",
+    "anything",
+    "silence_warnings",
+    "instance_variable_names",
+    "_fixture_path",
+    "copy_instance_variables_from",
+    "fixture_path?",
+    "has_entry",
+    "__marshal__",
+    "_fixture_table_names",
+    "__kind_of__",
+    "fixture_table_names?",
+    "test_add_rename",
+    "assert_equal",
+    "_fixture_class_names",
+    "fixture_class_names?",
+    "has_entries",
+    "_use_transactional_fixtures",
+    "people",
+    "test_rename_column_using_symbol_arguments",
+    "use_transactional_fixtures?",
+    "instance_eval",
+    "blank?",
+    "with_warnings",
+    "__nil__",
+    "load",
+    "metaclass",
+    "_use_instantiated_fixtures",
+    "has_key",
+    "class_eval",
+    "present?",
+    "test_rename_column",
+    "teardown",
+    "use_instantiated_fixtures?",
+    "method_name",
+    "silence_stderr",
+    "presence",
+    "test_rename_column_preserves_default_value_not_null",
+    "silence_stream",
+    "_pre_loaded_fixtures",
+    "__metaclass__",
+    "__fixnum__",
+    "pre_loaded_fixtures?",
+    "has_value",
+    "suppress",
+    "to_yaml_properties",
+    "test_rename_nonexistent_column",
+    "test_add_index",
+    "includes",
+    "find_correlate_in",
+    "equality_predicate_sql",
+    "assert_nothing_raised",
+    "let",
+    "not_predicate_sql",
+    "test_rename_column_with_sql_reserved_word",
+    "singleton_class",
+    "test_rename_column_with_an_index",
+    "display",
+    "taguri",
+    "to_yaml_style",
+    "test_remove_column_with_index",
+    "size",
+    "current_adapter?",
+    "test_remove_column_with_multi_column_index",
+    "respond_to?",
+    "test_change_type_of_not_null_column",
+    "is_a",
+    "to_a",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "require_library_or_gem",
+    "setup_fixtures",
+    "equal?",
+    "teardown_fixtures",
+    "nil?",
+    "fixture_table_names",
+    "fixture_class_names",
+    "test_create_table_without_id",
+    "use_transactional_fixtures",
+    "test_add_column_with_primary_key_attribute",
+    "repair_validations",
+    "use_instantiated_fixtures",
+    "instance_of?",
+    "test_create_table_adds_id",
+    "test_rename_table",
+    "pre_loaded_fixtures",
+    "to_enum",
+    "test_create_table_with_not_null_column",
+    "instance_of",
+    "test_change_column_nullability",
+    "optionally",
+    "test_rename_table_with_an_index",
+    "run",
+    "test_change_column",
+    "default_test",
+    "assert_raise",
+    "test_create_table_with_defaults",
+    "assert_nil",
+    "flunk",
+    "regexp_matches",
+    "duplicable?",
+    "reset_mocha",
+    "stubba_method",
+    "filter_backtrace",
+    "test_create_table_with_limits",
+    "responds_with",
+    "stubba_object",
+    "test_change_column_with_nil_default",
+    "assert_block",
+    "__show__",
+    "assert_date_from_db",
+    "__respond_to_eh__",
+    "run_in_transaction?",
+    "inspect",
+    "assert_sql",
+    "test_change_column_with_new_default",
+    "yaml_equivalent",
+    "build_message",
+    "to_s",
+    "test_change_column_default",
+    "assert_queries",
+    "pending",
+    "as_json",
+    "assert_no_queries",
+    "test_change_column_quotes_column_names",
+    "assert_match",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "methods",
+    "connection_allow_concurrency_setup",
+    "connection_allow_concurrency_teardown",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "__send__",
+    "make_connection",
+    "assert_raises",
+    "tap",
+    "with_kcode",
+    "assert_instance_of",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "assert_respond_to",
+    "test_change_column_default_to_null",
+    "assert_same",
+    "__extend__",
+  ]
+
+  LargeTestArraySorted = [
+    "test_add_column_not_null_with_default",
+    "test_add_column_with_precision_and_scale",
+    "test_add_column_with_primary_key_attribute",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "test_add_index",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "test_add_rename",
+    "test_add_table",
+    "test_add_table_with_decimals",
+    "test_change_column",
+    "test_change_column_default",
+    "test_change_column_default_to_null",
+    "test_change_column_nullability",
+    "test_change_column_quotes_column_names",
+    "test_change_column_with_new_default",
+    "test_change_column_with_nil_default",
+    "test_change_type_of_not_null_column",
+    "test_create_table_adds_id",
+    "test_create_table_with_binary_column",
+    "test_create_table_with_custom_sequence_name",
+    "test_create_table_with_defaults",
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_create_table_with_limits",
+    "test_create_table_with_not_null_column",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "test_create_table_without_a_block",
+    "test_create_table_without_id",
+    "test_finds_migrations",
+    "test_finds_pending_migrations",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "test_migrator",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_double_down",
+    "test_migrator_double_up",
+    "test_migrator_forward",
+    "test_migrator_going_down_due_to_version_target",
+    "test_migrator_one_down",
+    "test_migrator_one_up",
+    "test_migrator_one_up_one_down",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "test_migrator_rollback",
+    "test_migrator_verbosity",
+    "test_migrator_verbosity_off",
+    "test_migrator_with_duplicate_names",
+    "test_migrator_with_duplicates",
+    "test_migrator_with_missing_version_numbers",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "test_native_types",
+    "test_only_loads_pending_migrations",
+    "test_proper_table_name",
+    "test_relative_migrations",
+    "test_remove_column_with_index",
+    "test_remove_column_with_multi_column_index",
+    "test_rename_column",
+    "test_rename_column_preserves_default_value_not_null",
+    "test_rename_column_using_symbol_arguments",
+    "test_rename_column_with_an_index",
+    "test_rename_column_with_sql_reserved_word",
+    "test_rename_nonexistent_column",
+    "test_rename_table",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "test_rename_table_with_an_index",
+    "test_schema_migrations_table_name",
+    "test_target_version_zero_should_run_only_once",
+  ]
+
+  class PrivateToAry
+    private
+
+    def to_ary
+      [1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/core/array/fixtures/encoded_strings.rb b/spec/ruby/core/array/fixtures/encoded_strings.rb
new file mode 100644
index 0000000000..b5888d86ae
--- /dev/null
+++ b/spec/ruby/core/array/fixtures/encoded_strings.rb
@@ -0,0 +1,69 @@
+# encoding: utf-8
+module ArraySpecs
+  def self.array_with_usascii_and_7bit_utf8_strings
+    [
+      'foo'.dup.force_encoding('US-ASCII'),
+      'bar'
+    ]
+  end
+
+  def self.array_with_usascii_and_utf8_strings
+    [
+      'foo'.dup.force_encoding('US-ASCII'),
+      'báz'
+    ]
+  end
+
+  def self.array_with_7bit_utf8_and_usascii_strings
+    [
+      'bar',
+      'foo'.dup.force_encoding('US-ASCII')
+    ]
+  end
+
+  def self.array_with_utf8_and_usascii_strings
+    [
+      'báz',
+      'bar',
+      'foo'.dup.force_encoding('US-ASCII')
+    ]
+  end
+
+  def self.array_with_usascii_and_utf8_strings
+    [
+      'foo'.dup.force_encoding('US-ASCII'),
+      'bar',
+      'báz'
+    ]
+  end
+
+  def self.array_with_utf8_and_7bit_binary_strings
+    [
+      'bar',
+      'báz',
+      'foo'.dup.force_encoding('BINARY')
+    ]
+  end
+
+  def self.array_with_utf8_and_binary_strings
+    [
+      'bar',
+      'báz',
+      [255].pack('C').force_encoding('BINARY')
+    ]
+  end
+
+  def self.array_with_usascii_and_7bit_binary_strings
+    [
+      'bar'.dup.force_encoding('US-ASCII'),
+      'foo'.dup.force_encoding('BINARY')
+    ]
+  end
+
+  def self.array_with_usascii_and_binary_strings
+    [
+      'bar'.dup.force_encoding('US-ASCII'),
+      [255].pack('C').force_encoding('BINARY')
+    ]
+  end
+end
diff --git a/spec/ruby/core/array/flatten_spec.rb b/spec/ruby/core/array/flatten_spec.rb
new file mode 100644
index 0000000000..272406b8f9
--- /dev/null
+++ b/spec/ruby/core/array/flatten_spec.rb
@@ -0,0 +1,266 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#flatten" do
+  it "returns a one-dimensional flattening recursively" do
+    [[[1, [2, 3]],[2, 3, [4, [4, [5, 5]], [1, 2, 3]]], [4]], []].flatten.should == [1, 2, 3, 2, 3, 4, 4, 5, 5, 1, 2, 3, 4]
+  end
+
+  it "takes an optional argument that determines the level of recursion" do
+    [ 1, 2, [3, [4, 5] ] ].flatten(1).should == [1, 2, 3, [4, 5]]
+  end
+
+  it "returns dup when the level of recursion is 0" do
+    a = [ 1, 2, [3, [4, 5] ] ]
+    a.flatten(0).should == a
+    a.flatten(0).should_not.equal?(a)
+  end
+
+  it "ignores negative levels" do
+    [ 1, 2, [ 3, 4, [5, 6] ] ].flatten(-1).should == [1, 2, 3, 4, 5, 6]
+    [ 1, 2, [ 3, 4, [5, 6] ] ].flatten(-10).should == [1, 2, 3, 4, 5, 6]
+  end
+
+  it "tries to convert passed Objects to Integers using #to_int" do
+    obj = mock("Converted to Integer")
+    obj.should_receive(:to_int).and_return(1)
+
+    [ 1, 2, [3, [4, 5] ] ].flatten(obj).should == [1, 2, 3, [4, 5]]
+  end
+
+  it "raises a TypeError when the passed Object can't be converted to an Integer" do
+    obj = mock("Not converted")
+    -> { [ 1, 2, [3, [4, 5] ] ].flatten(obj) }.should.raise(TypeError)
+  end
+
+  it "does not call flatten on elements" do
+    obj = mock('[1,2]')
+    obj.should_not_receive(:flatten)
+    [obj, obj].flatten.should == [obj, obj]
+
+    obj = [5, 4]
+    obj.should_not_receive(:flatten)
+    [obj, obj].flatten.should == [5, 4, 5, 4]
+  end
+
+  it "raises an ArgumentError on recursive arrays" do
+    x = []
+    x << x
+    -> { x.flatten }.should.raise(ArgumentError)
+
+    x = []
+    y = []
+    x << y
+    y << x
+    -> { x.flatten }.should.raise(ArgumentError)
+  end
+
+  it "flattens any element which responds to #to_ary, using the return value of said method" do
+    x = mock("[3,4]")
+    x.should_receive(:to_ary).at_least(:once).and_return([3, 4])
+    [1, 2, x, 5].flatten.should == [1, 2, 3, 4, 5]
+
+    y = mock("MyArray[]")
+    y.should_receive(:to_ary).at_least(:once).and_return(ArraySpecs::MyArray[])
+    [y].flatten.should == []
+
+    z = mock("[2,x,y,5]")
+    z.should_receive(:to_ary).and_return([2, x, y, 5])
+    [1, z, 6].flatten.should == [1, 2, 3, 4, 5, 6]
+  end
+
+  it "does not call #to_ary on elements beyond the given level" do
+    obj = mock("1")
+    obj.should_not_receive(:to_ary)
+    [[obj]].flatten(1)
+  end
+
+  it "returns Array instance for Array subclasses" do
+    ArraySpecs::MyArray[].flatten.should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].flatten.should.instance_of?(Array)
+    ArraySpecs::MyArray[1, [2], 3].flatten.should.instance_of?(Array)
+    ArraySpecs::MyArray[1, [2, 3], 4].flatten.should == [1, 2, 3, 4]
+    [ArraySpecs::MyArray[1, 2, 3]].flatten.should.instance_of?(Array)
+  end
+
+  it "is not destructive" do
+    ary = [1, [2, 3]]
+    ary.flatten
+    ary.should == [1, [2, 3]]
+  end
+
+  describe "with a non-Array object in the Array" do
+    before :each do
+      @obj = mock("Array#flatten")
+      ScratchPad.record []
+    end
+
+    it "does not call #to_ary if the method is not defined" do
+      [@obj].flatten.should == [@obj]
+    end
+
+    it "does not raise an exception if #to_ary returns nil" do
+      @obj.should_receive(:to_ary).and_return(nil)
+      [@obj].flatten.should == [@obj]
+    end
+
+    it "raises a TypeError if #to_ary does not return an Array" do
+      @obj.should_receive(:to_ary).and_return(1)
+      -> { [@obj].flatten }.should.raise(TypeError)
+    end
+
+    it "calls respond_to_missing?(:to_ary, true) to try coercing" do
+      def @obj.respond_to_missing?(*args) ScratchPad << args; false end
+      [@obj].flatten.should == [@obj]
+      ScratchPad.recorded.should == [[:to_ary, true]]
+    end
+
+    it "does not call #to_ary if not defined when #respond_to_missing? returns false" do
+      def @obj.respond_to_missing?(name, priv) ScratchPad << name; false end
+
+      [@obj].flatten.should == [@obj]
+      ScratchPad.recorded.should == [:to_ary]
+    end
+
+    it "calls #to_ary if not defined when #respond_to_missing? returns true" do
+      def @obj.respond_to_missing?(name, priv) ScratchPad << name; true end
+
+      -> { [@obj].flatten }.should.raise(NoMethodError)
+      ScratchPad.recorded.should == [:to_ary]
+    end
+
+    it "calls #method_missing if defined" do
+      @obj.should_receive(:method_missing).with(:to_ary).and_return([1, 2, 3])
+      [@obj].flatten.should == [1, 2, 3]
+    end
+  end
+
+  it "performs respond_to? and method_missing-aware checks when coercing elements to array" do
+    bo = BasicObject.new
+    [bo].flatten.should == [bo]
+
+    def bo.method_missing(name, *)
+      [1,2]
+    end
+
+    [bo].flatten.should == [1,2]
+
+    def bo.respond_to?(name, *)
+      false
+    end
+
+    [bo].flatten.should == [bo]
+
+    def bo.respond_to?(name, *)
+      true
+    end
+
+    [bo].flatten.should == [1,2]
+  end
+end
+
+describe "Array#flatten!" do
+  it "modifies array to produce a one-dimensional flattening recursively" do
+    a = [[[1, [2, 3]],[2, 3, [4, [4, [5, 5]], [1, 2, 3]]], [4]], []]
+    a.flatten!
+    a.should == [1, 2, 3, 2, 3, 4, 4, 5, 5, 1, 2, 3, 4]
+  end
+
+  it "returns self if made some modifications" do
+    a = [[[1, [2, 3]],[2, 3, [4, [4, [5, 5]], [1, 2, 3]]], [4]], []]
+    a.flatten!.should.equal?(a)
+  end
+
+  it "returns nil if no modifications took place" do
+    a = [1, 2, 3]
+    a.flatten!.should == nil
+    a = [1, [2, 3]]
+    a.flatten!.should_not == nil
+  end
+
+  it "should not check modification by size" do
+    a = [1, 2, [3]]
+    a.flatten!.should_not == nil
+    a.should == [1, 2, 3]
+  end
+
+  it "takes an optional argument that determines the level of recursion" do
+    [ 1, 2, [3, [4, 5] ] ].flatten!(1).should == [1, 2, 3, [4, 5]]
+  end
+
+  # redmine #1440
+  it "returns nil when the level of recursion is 0" do
+    a = [ 1, 2, [3, [4, 5] ] ]
+    a.flatten!(0).should == nil
+  end
+
+  it "treats negative levels as no arguments" do
+    [ 1, 2, [ 3, 4, [5, 6] ] ].flatten!(-1).should == [1, 2, 3, 4, 5, 6]
+    [ 1, 2, [ 3, 4, [5, 6] ] ].flatten!(-10).should == [1, 2, 3, 4, 5, 6]
+  end
+
+  it "tries to convert passed Objects to Integers using #to_int" do
+    obj = mock("Converted to Integer")
+    obj.should_receive(:to_int).and_return(1)
+
+    [ 1, 2, [3, [4, 5] ] ].flatten!(obj).should == [1, 2, 3, [4, 5]]
+  end
+
+  it "raises a TypeError when the passed Object can't be converted to an Integer" do
+    obj = mock("Not converted")
+    -> { [ 1, 2, [3, [4, 5] ] ].flatten!(obj) }.should.raise(TypeError)
+  end
+
+  it "does not call flatten! on elements" do
+    obj = mock('[1,2]')
+    obj.should_not_receive(:flatten!)
+    [obj, obj].flatten!.should == nil
+
+    obj = [5, 4]
+    obj.should_not_receive(:flatten!)
+    [obj, obj].flatten!.should == [5, 4, 5, 4]
+  end
+
+  it "raises an ArgumentError on recursive arrays" do
+    x = []
+    x << x
+    -> { x.flatten! }.should.raise(ArgumentError)
+
+    x = []
+    y = []
+    x << y
+    y << x
+    -> { x.flatten! }.should.raise(ArgumentError)
+  end
+
+  it "flattens any elements which responds to #to_ary, using the return value of said method" do
+    x = mock("[3,4]")
+    x.should_receive(:to_ary).at_least(:once).and_return([3, 4])
+    [1, 2, x, 5].flatten!.should == [1, 2, 3, 4, 5]
+
+    y = mock("MyArray[]")
+    y.should_receive(:to_ary).at_least(:once).and_return(ArraySpecs::MyArray[])
+    [y].flatten!.should == []
+
+    z = mock("[2,x,y,5]")
+    z.should_receive(:to_ary).and_return([2, x, y, 5])
+    [1, z, 6].flatten!.should == [1, 2, 3, 4, 5, 6]
+
+    ary = [ArraySpecs::MyArray[1, 2, 3]]
+    ary.flatten!
+    ary.should.instance_of?(Array)
+    ary.should == [1, 2, 3]
+  end
+
+  it "raises a FrozenError on frozen arrays when the array is modified" do
+    nested_ary = [1, 2, []]
+    nested_ary.freeze
+    -> { nested_ary.flatten! }.should.raise(FrozenError)
+  end
+
+  # see [ruby-core:23663]
+  it "raises a FrozenError on frozen arrays when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.flatten! }.should.raise(FrozenError)
+    -> { ArraySpecs.empty_frozen_array.flatten! }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/frozen_spec.rb b/spec/ruby/core/array/frozen_spec.rb
new file mode 100644
index 0000000000..3ba54be46b
--- /dev/null
+++ b/spec/ruby/core/array/frozen_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#frozen?" do
+  it "returns true if array is frozen" do
+    a = [1, 2, 3]
+    a.should_not.frozen?
+    a.freeze
+    a.should.frozen?
+  end
+
+  it "returns false for an array being sorted by #sort" do
+    a = [1, 2, 3]
+    a.sort { |x,y| a.should_not.frozen?; x <=> y }
+  end
+end
diff --git a/spec/ruby/core/array/hash_spec.rb b/spec/ruby/core/array/hash_spec.rb
new file mode 100644
index 0000000000..3b7b6d5bed
--- /dev/null
+++ b/spec/ruby/core/array/hash_spec.rb
@@ -0,0 +1,83 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#hash" do
+  it "returns the same fixnum for arrays with the same content" do
+    [].respond_to?(:hash).should == true
+
+    [[], [1, 2, 3]].each do |ary|
+      ary.hash.should == ary.dup.hash
+      ary.hash.should.instance_of?(Integer)
+    end
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    -> { empty.hash }.should_not.raise
+
+    array = ArraySpecs.recursive_array
+    -> { array.hash }.should_not.raise
+  end
+
+  it "returns the same hash for equal recursive arrays" do
+    rec = []; rec << rec
+    rec.hash.should == [rec].hash
+    rec.hash.should == [[rec]].hash
+    # This is because rec.eql?([[rec]])
+    # Remember that if two objects are eql?
+    # then the need to have the same hash
+    # Check the Array#eql? specs!
+  end
+
+  it "returns the same hash for equal recursive arrays through hashes" do
+    h = {} ; rec = [h] ; h[:x] = rec
+    rec.hash.should == [h].hash
+    rec.hash.should == [{x: rec}].hash
+    # Like above, this is because rec.eql?([{x: rec}])
+  end
+
+  it "calls to_int on result of calling hash on each element" do
+    ary = Array.new(5) do
+      obj = mock('0')
+      obj.should_receive(:hash).and_return(obj)
+      obj.should_receive(:to_int).and_return(0)
+      obj
+    end
+
+    ary.hash
+
+
+    hash = mock('1')
+    hash.should_receive(:to_int).and_return(1.hash)
+
+    obj = mock('@hash')
+    obj.instance_variable_set(:@hash, hash)
+    def obj.hash() @hash end
+
+    [obj].hash.should == [1].hash
+  end
+
+  it "ignores array class differences" do
+    ArraySpecs::MyArray[].hash.should == [].hash
+    ArraySpecs::MyArray[1, 2].hash.should == [1, 2].hash
+  end
+
+  it "returns same hash code for arrays with the same content" do
+    a = [1, 2, 3, 4]
+    a.fill 'a', 0..3
+    b = %w|a a a a|
+    a.hash.should == b.hash
+  end
+
+  it "returns the same value if arrays are #eql?" do
+    a = [1, 2, 3, 4]
+    a.fill 'a', 0..3
+    b = %w|a a a a|
+    a.hash.should == b.hash
+    a.should.eql?(b)
+  end
+
+  it "produces different hashes for nested arrays with different values and empty terminator" do
+    [1, [1, []]].hash.should_not == [2, [2, []]].hash
+  end
+end
diff --git a/spec/ruby/core/array/include_spec.rb b/spec/ruby/core/array/include_spec.rb
new file mode 100644
index 0000000000..227173218f
--- /dev/null
+++ b/spec/ruby/core/array/include_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#include?" do
+  it "returns true if object is present, false otherwise" do
+    [1, 2, "a", "b"].include?("c").should == false
+    [1, 2, "a", "b"].include?("a").should == true
+  end
+
+  it "determines presence by using element == obj" do
+    o = mock('')
+
+    [1, 2, "a", "b"].include?(o).should == false
+
+    def o.==(other); other == 'a'; end
+
+    [1, 2, o, "b"].include?('a').should == true
+
+    [1, 2.0, 3].include?(2).should == true
+  end
+
+  it "calls == on elements from left to right until success" do
+    key = "x"
+    one = mock('one')
+    two = mock('two')
+    three = mock('three')
+    one.should_receive(:==).any_number_of_times.and_return(false)
+    two.should_receive(:==).any_number_of_times.and_return(true)
+    three.should_not_receive(:==)
+    ary = [one, two, three]
+    ary.include?(key).should == true
+  end
+end
diff --git a/spec/ruby/core/array/index_spec.rb b/spec/ruby/core/array/index_spec.rb
new file mode 100644
index 0000000000..b66cb6eb53
--- /dev/null
+++ b/spec/ruby/core/array/index_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+
+describe "Array#index" do
+  it "is an alias of Array#find_index" do
+    Array.instance_method(:index).should == Array.instance_method(:find_index)
+  end
+end
diff --git a/spec/ruby/core/array/initialize_spec.rb b/spec/ruby/core/array/initialize_spec.rb
new file mode 100644
index 0000000000..19ee37825e
--- /dev/null
+++ b/spec/ruby/core/array/initialize_spec.rb
@@ -0,0 +1,158 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#initialize" do
+  before :each do
+    ScratchPad.clear
+  end
+
+  it "is private" do
+    Array.private_instance_methods(false).should.include?(:initialize)
+  end
+
+  it "is called on subclasses" do
+    b = ArraySpecs::SubArray.new :size_or_array, :obj
+
+    b.should == []
+    ScratchPad.recorded.should == [:size_or_array, :obj]
+  end
+
+  it "preserves the object's identity even when changing its value" do
+    a = [1, 2, 3]
+    a.send(:initialize).should.equal?(a)
+    a.should_not == [1, 2, 3]
+  end
+
+  it "raises an ArgumentError if passed 3 or more arguments" do
+    -> do
+      [1, 2].send :initialize, 1, 'x', true
+    end.should.raise(ArgumentError)
+    -> do
+      [1, 2].send(:initialize, 1, 'x', true) {}
+    end.should.raise(ArgumentError)
+  end
+
+  it "raises a FrozenError on frozen arrays" do
+    -> do
+      ArraySpecs.frozen_array.send :initialize
+    end.should.raise(FrozenError)
+    -> do
+      ArraySpecs.frozen_array.send :initialize, ArraySpecs.frozen_array
+    end.should.raise(FrozenError)
+  end
+
+  it "calls #to_ary to convert the value to an array, even if it's private" do
+    a = ArraySpecs::PrivateToAry.new
+    [].send(:initialize, a).should == [1, 2, 3]
+  end
+end
+
+describe "Array#initialize with no arguments" do
+  it "makes the array empty" do
+    [1, 2, 3].send(:initialize).should.empty?
+  end
+
+  it "does not use the given block" do
+    -> {
+      -> { [1, 2, 3].send(:initialize) { raise } }.should_not.raise
+    }.should complain(/#{__FILE__}:#{__LINE__-1}: warning: given block not used/, verbose: true)
+  end
+end
+
+describe "Array#initialize with (array)" do
+  it "replaces self with the other array" do
+    b = [4, 5, 6]
+    [1, 2, 3].send(:initialize, b).should == b
+  end
+
+  it "does not use the given block" do
+    ->{ [1, 2, 3].send(:initialize) { raise } }.should_not.raise
+  end
+
+  it "calls #to_ary to convert the value to an array" do
+    a = mock("array")
+    a.should_receive(:to_ary).and_return([1, 2])
+    a.should_not_receive(:to_int)
+    [].send(:initialize, a).should == [1, 2]
+  end
+
+  it "does not call #to_ary on instances of Array or subclasses of Array" do
+    a = [1, 2]
+    a.should_not_receive(:to_ary)
+    [].send(:initialize, a).should == a
+  end
+
+  it "raises a TypeError if an Array type argument and a default object" do
+    -> { [].send(:initialize, [1, 2], 1) }.should.raise(TypeError)
+  end
+end
+
+describe "Array#initialize with (size, object=nil)" do
+  it "sets the array to size and fills with the object" do
+    a = []
+    obj = [3]
+    a.send(:initialize, 2, obj).should == [obj, obj]
+    a[0].should.equal?(obj)
+    a[1].should.equal?(obj)
+
+    b = []
+    b.send(:initialize, 3, 14).should == [14, 14, 14]
+    b.should == [14, 14, 14]
+  end
+
+  it "sets the array to size and fills with nil when object is omitted" do
+    [].send(:initialize, 3).should == [nil, nil, nil]
+  end
+
+  it "raises an ArgumentError if size is negative" do
+    -> { [].send(:initialize, -1, :a) }.should.raise(ArgumentError)
+    -> { [].send(:initialize, -1) }.should.raise(ArgumentError)
+  end
+
+  it "raises an ArgumentError if size is too large" do
+    -> { [].send(:initialize, fixnum_max+1) }.should.raise(ArgumentError)
+  end
+
+  it "calls #to_int to convert the size argument to an Integer when object is given" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    [].send(:initialize, obj, :a).should == [:a]
+  end
+
+  it "calls #to_int to convert the size argument to an Integer when object is not given" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    [].send(:initialize, obj).should == [nil]
+  end
+
+  it "raises a TypeError if the size argument is not an Integer type" do
+    obj = mock('nonnumeric')
+    obj.stub!(:to_ary).and_return([1, 2])
+    ->{ [].send(:initialize, obj, :a) }.should.raise(TypeError)
+  end
+
+  it "yields the index of the element and sets the element to the value of the block" do
+    [].send(:initialize, 3) { |i| i.to_s }.should == ['0', '1', '2']
+  end
+
+  it "uses the block value instead of using the default value" do
+    -> {
+      @result = [].send(:initialize, 3, :obj) { |i| i.to_s }
+    }.should complain(/block supersedes default value argument/)
+    @result.should == ['0', '1', '2']
+  end
+
+  it "returns the value passed to break" do
+    [].send(:initialize, 3) { break :a }.should == :a
+  end
+
+  it "sets the array to the values returned by the block before break is executed" do
+    a = [1, 2, 3]
+    a.send(:initialize, 3) do |i|
+      break if i == 2
+      i.to_s
+    end
+
+    a.should == ['0', '1']
+  end
+end
diff --git a/spec/ruby/core/array/insert_spec.rb b/spec/ruby/core/array/insert_spec.rb
new file mode 100644
index 0000000000..38e132fd25
--- /dev/null
+++ b/spec/ruby/core/array/insert_spec.rb
@@ -0,0 +1,78 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#insert" do
+  it "returns self" do
+    ary = []
+    ary.insert(0).should.equal?(ary)
+    ary.insert(0, :a).should.equal?(ary)
+  end
+
+  it "inserts objects before the element at index for non-negative index" do
+    ary = []
+    ary.insert(0, 3).should == [3]
+    ary.insert(0, 1, 2).should == [1, 2, 3]
+    ary.insert(0).should == [1, 2, 3]
+
+    # Let's just assume insert() always modifies the array from now on.
+    ary.insert(1, 'a').should == [1, 'a', 2, 3]
+    ary.insert(0, 'b').should == ['b', 1, 'a', 2, 3]
+    ary.insert(5, 'c').should == ['b', 1, 'a', 2, 3, 'c']
+    ary.insert(7, 'd').should == ['b', 1, 'a', 2, 3, 'c', nil, 'd']
+    ary.insert(10, 5, 4).should == ['b', 1, 'a', 2, 3, 'c', nil, 'd', nil, nil, 5, 4]
+  end
+
+  it "appends objects to the end of the array for index == -1" do
+    [1, 3, 3].insert(-1, 2, 'x', 0.5).should == [1, 3, 3, 2, 'x', 0.5]
+  end
+
+  it "inserts objects after the element at index with negative index" do
+    ary = []
+    ary.insert(-1, 3).should == [3]
+    ary.insert(-2, 2).should == [2, 3]
+    ary.insert(-3, 1).should == [1, 2, 3]
+    ary.insert(-2, -3).should == [1, 2, -3, 3]
+    ary.insert(-1, []).should == [1, 2, -3, 3, []]
+    ary.insert(-2, 'x', 'y').should == [1, 2, -3, 3, 'x', 'y', []]
+    ary = [1, 2, 3]
+  end
+
+  it "pads with nils if the index to be inserted to is past the end" do
+    [].insert(5, 5).should == [nil, nil, nil, nil, nil, 5]
+  end
+
+  it "can insert before the first element with a negative index" do
+    [1, 2, 3].insert(-4, -3).should == [-3, 1, 2, 3]
+  end
+
+  it "raises an IndexError if the negative index is out of bounds" do
+    -> { [].insert(-2, 1)  }.should.raise(IndexError)
+    -> { [1].insert(-3, 2) }.should.raise(IndexError)
+  end
+
+  it "does nothing of no object is passed" do
+    [].insert(0).should == []
+    [].insert(-1).should == []
+    [].insert(10).should == []
+    [].insert(-2).should == []
+  end
+
+  it "tries to convert the passed position argument to an Integer using #to_int" do
+    obj = mock('2')
+    obj.should_receive(:to_int).and_return(2)
+    [].insert(obj, 'x').should == [nil, nil, 'x']
+  end
+
+  it "raises an ArgumentError if no argument passed" do
+    -> { [].insert() }.should.raise(ArgumentError)
+  end
+
+  it "raises a FrozenError on frozen arrays when the array is modified" do
+    -> { ArraySpecs.frozen_array.insert(0, 'x') }.should.raise(FrozenError)
+  end
+
+  # see [ruby-core:23666]
+  it "raises a FrozenError on frozen arrays when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.insert(0) }.should.raise(FrozenError)
+  end
+end
diff --git a/spec/ruby/core/array/inspect_spec.rb b/spec/ruby/core/array/inspect_spec.rb
new file mode 100644
index 0000000000..e5dca82889
--- /dev/null
+++ b/spec/ruby/core/array/inspect_spec.rb
@@ -0,0 +1,108 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#inspect" do
+  it "returns a string" do
+    [1, 2, 3].inspect.should.instance_of?(String)
+  end
+
+  it "returns '[]' for an empty Array" do
+    [].inspect.should == "[]"
+  end
+
+  it "calls inspect on its elements and joins the results with commas" do
+    items = Array.new(3) do |i|
+      obj = mock(i.to_s)
+      obj.should_receive(:inspect).and_return(i.to_s)
+      obj
+    end
+    items.inspect.should == "[0, 1, 2]"
+  end
+
+  it "does not call #to_s on a String returned from #inspect" do
+    str = +"abc"
+    str.should_not_receive(:to_s)
+
+    [str].inspect.should == '["abc"]'
+  end
+
+  it "calls #to_s on the object returned from #inspect if the Object isn't a String" do
+    obj = mock("Array#inspect/to_s calls #to_s")
+    obj.should_receive(:inspect).and_return(obj)
+    obj.should_receive(:to_s).and_return("abc")
+
+    [obj].inspect.should == "[abc]"
+  end
+
+  it "does not call #to_str on the object returned from #inspect when it is not a String" do
+    obj = mock("Array#inspect/to_s does not call #to_str")
+    obj.should_receive(:inspect).and_return(obj)
+    obj.should_not_receive(:to_str)
+
+    [obj].inspect.should =~ /^\[#<MockObject:0x[0-9a-f]+>\]$/
+  end
+
+  it "does not call #to_str on the object returned from #to_s when it is not a String" do
+    obj = mock("Array#inspect/to_s does not call #to_str on #to_s result")
+    obj.should_receive(:inspect).and_return(obj)
+    obj.should_receive(:to_s).and_return(obj)
+    obj.should_not_receive(:to_str)
+
+    [obj].inspect.should =~ /^\[#<MockObject:0x[0-9a-f]+>\]$/
+  end
+
+  it "does not swallow exceptions raised by #to_s" do
+    obj = mock("Array#inspect/to_s does not swallow #to_s exceptions")
+    obj.should_receive(:inspect).and_return(obj)
+    obj.should_receive(:to_s).and_raise(Exception)
+
+    -> { [obj].inspect }.should.raise(Exception)
+  end
+
+  it "represents a recursive element with '[...]'" do
+    ArraySpecs.recursive_array.inspect.should == "[1, \"two\", 3.0, [...], [...], [...], [...], [...]]"
+    ArraySpecs.head_recursive_array.inspect.should == "[[...], [...], [...], [...], [...], 1, \"two\", 3.0]"
+    ArraySpecs.empty_recursive_array.inspect.should == "[[...]]"
+  end
+
+  describe "with encoding" do
+    before :each do
+      @default_external_encoding = Encoding.default_external
+    end
+
+    after :each do
+      Encoding.default_external = @default_external_encoding
+    end
+
+    it "returns a US-ASCII string for an empty Array" do
+      [].inspect.encoding.should == Encoding::US_ASCII
+    end
+
+    it "use the default external encoding if it is ascii compatible" do
+      Encoding.default_external = Encoding.find('UTF-8')
+
+      utf8 = "utf8".encode("UTF-8")
+      jp   = "jp".encode("EUC-JP")
+      array = [jp, utf8]
+
+      array.inspect.encoding.name.should == "UTF-8"
+    end
+
+    it "use US-ASCII encoding if the default external encoding is not ascii compatible" do
+      Encoding.default_external = Encoding.find('UTF-32')
+
+      utf8 = "utf8".encode("UTF-8")
+      jp   = "jp".encode("EUC-JP")
+      array = [jp, utf8]
+
+      array.inspect.encoding.name.should == "US-ASCII"
+    end
+
+    it "does not raise if inspected result is not default external encoding" do
+      utf_16be = mock(+"utf_16be")
+      utf_16be.should_receive(:inspect).and_return(%<"utf_16be \u3042">.encode(Encoding::UTF_16BE))
+
+      [utf_16be].inspect.should == '["utf_16be \u3042"]'
+    end
+  end
+end
diff --git a/spec/ruby/core/array/intersect_spec.rb b/spec/ruby/core/array/intersect_spec.rb
new file mode 100644
index 0000000000..456aa26c6e
--- /dev/null
+++ b/spec/ruby/core/array/intersect_spec.rb
@@ -0,0 +1,64 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe 'Array#intersect?' do
+  describe 'when at least one element in two Arrays is the same' do
+    it 'returns true' do
+      [1, 2].intersect?([2, 3, 4]).should == true
+      [2, 3, 4].intersect?([1, 2]).should == true
+    end
+  end
+
+  describe 'when there are no elements in common between two Arrays' do
+    it 'returns false' do
+      [0, 1, 2].intersect?([3, 4]).should == false
+      [3, 4].intersect?([0, 1, 2]).should == false
+      [3, 4].intersect?([]).should == false
+      [].intersect?([0, 1, 2]).should == false
+    end
+  end
+
+  it "tries to convert the passed argument to an Array using #to_ary" do
+    obj = mock('[1,2,3]')
+    obj.should_receive(:to_ary).and_return([1, 2, 3])
+
+    [1, 2].intersect?(obj).should == true
+  end
+
+  it "determines equivalence between elements in the sense of eql?" do
+    obj1 = mock('1')
+    obj2 = mock('2')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.stub!(:eql?).and_return(true)
+    obj2.stub!(:eql?).and_return(true)
+
+    [obj1].intersect?([obj2]).should == true
+
+    obj1 = mock('3')
+    obj2 = mock('4')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.stub!(:eql?).and_return(false)
+    obj2.stub!(:eql?).and_return(false)
+
+    [obj1].intersect?([obj2]).should == false
+  end
+
+  it "does not call to_ary on array subclasses" do
+    [5, 6].intersect?(ArraySpecs::ToAryArray[1, 2, 5, 6]).should == true
+  end
+
+  it "properly handles an identical item even when its #eql? isn't reflexive" do
+    x = mock('x')
+    x.stub!(:hash).and_return(42)
+    x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
+
+    [x].intersect?([x]).should == true
+  end
+
+  it "has semantic of !(a & b).empty?" do
+    [].intersect?([]).should == false
+    [nil].intersect?([nil]).should == true
+  end
+end
diff --git a/spec/ruby/core/array/intersection_spec.rb b/spec/ruby/core/array/intersection_spec.rb
new file mode 100644
index 0000000000..e01a68d389
--- /dev/null
+++ b/spec/ruby/core/array/intersection_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/intersection'
+
+describe "Array#&" do
+  it_behaves_like :array_intersection, :&
+end
+
+describe "Array#intersection" do
+  it_behaves_like :array_intersection, :intersection
+
+  it "accepts multiple arguments" do
+    [1, 2, 3, 4].intersection([1, 2, 3], [2, 3, 4]).should == [2, 3]
+  end
+
+  it "preserves elements order from original array" do
+    [1, 2, 3, 4].intersection([3, 2, 1]).should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/array/join_spec.rb b/spec/ruby/core/array/join_spec.rb
new file mode 100644
index 0000000000..3b4946a99f
--- /dev/null
+++ b/spec/ruby/core/array/join_spec.rb
@@ -0,0 +1,146 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/join'
+
+describe "Array#join" do
+  it_behaves_like :array_join_with_string_separator,  :join
+
+  it "does not separate elements when the passed separator is nil" do
+    [1, 2, 3].join(nil).should == '123'
+  end
+
+  it "calls #to_str to convert the separator to a String" do
+    sep = mock("separator")
+    sep.should_receive(:to_str).and_return(", ")
+    [1, 2].join(sep).should == "1, 2"
+  end
+
+  it "does not call #to_str on the separator if the array is empty" do
+    sep = mock("separator")
+    sep.should_not_receive(:to_str)
+    [].join(sep).should == ""
+  end
+
+  it "raises a TypeError if the separator cannot be coerced to a String by calling #to_str" do
+    obj = mock("not a string")
+    -> { [1, 2].join(obj) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed false as the separator" do
+    -> { [1, 2].join(false) }.should.raise(TypeError)
+  end
+end
+
+describe "Array#join with default separator" do
+  before :each do
+    @separator = $,
+  end
+
+  after :each do
+    $, = @separator
+  end
+
+  it "returns an empty string if the Array is empty" do
+    [].join.should == ''
+  end
+
+  it "returns a US-ASCII string for an empty Array" do
+    [].join.encoding.should == Encoding::US_ASCII
+  end
+
+  it "returns a string formed by concatenating each String element separated by $," do
+    suppress_warning {
+      $, = " | "
+      ["1", "2", "3"].join.should == "1 | 2 | 3"
+    }
+  end
+
+  it "attempts coercion via #to_str first" do
+    obj = mock('foo')
+    obj.should_receive(:to_str).any_number_of_times.and_return("foo")
+    [obj].join.should == "foo"
+  end
+
+  it "attempts coercion via #to_ary second" do
+    obj = mock('foo')
+    obj.should_receive(:to_str).any_number_of_times.and_return(nil)
+    obj.should_receive(:to_ary).any_number_of_times.and_return(["foo"])
+    [obj].join.should == "foo"
+  end
+
+  it "attempts coercion via #to_s third" do
+    obj = mock('foo')
+    obj.should_receive(:to_str).any_number_of_times.and_return(nil)
+    obj.should_receive(:to_ary).any_number_of_times.and_return(nil)
+    obj.should_receive(:to_s).any_number_of_times.and_return("foo")
+    [obj].join.should == "foo"
+  end
+
+  it "raises a NoMethodError if an element does not respond to #to_str, #to_ary, or #to_s" do
+    obj = mock('o')
+    class << obj; undef :to_s; end
+    -> { [1, obj].join }.should.raise(NoMethodError)
+  end
+
+  it "raises an ArgumentError when the Array is recursive" do
+    -> { ArraySpecs.recursive_array.join }.should.raise(ArgumentError)
+    -> { ArraySpecs.head_recursive_array.join }.should.raise(ArgumentError)
+    -> { ArraySpecs.empty_recursive_array.join }.should.raise(ArgumentError)
+  end
+
+  it "uses the first encoding when other strings are compatible" do
+    ary1 = ArraySpecs.array_with_7bit_utf8_and_usascii_strings
+    ary2 = ArraySpecs.array_with_usascii_and_7bit_utf8_strings
+    ary3 = ArraySpecs.array_with_utf8_and_7bit_binary_strings
+    ary4 = ArraySpecs.array_with_usascii_and_7bit_binary_strings
+
+    ary1.join.encoding.should == Encoding::UTF_8
+    ary2.join.encoding.should == Encoding::US_ASCII
+    ary3.join.encoding.should == Encoding::UTF_8
+    ary4.join.encoding.should == Encoding::US_ASCII
+  end
+
+  it "uses the widest common encoding when other strings are incompatible" do
+    ary1 = ArraySpecs.array_with_utf8_and_usascii_strings
+    ary2 = ArraySpecs.array_with_usascii_and_utf8_strings
+
+    ary1.join.encoding.should == Encoding::UTF_8
+    ary2.join.encoding.should == Encoding::UTF_8
+  end
+
+  it "fails for arrays with incompatibly-encoded strings" do
+    ary_utf8_bad_binary = ArraySpecs.array_with_utf8_and_binary_strings
+
+    -> { ary_utf8_bad_binary.join }.should.raise(EncodingError)
+  end
+
+  context "when $, is not nil" do
+    before do
+      suppress_warning do
+        $, = '*'
+      end
+    end
+
+    it "warns" do
+      -> { [].join }.should complain(/warning: \$, is set to non-nil value/)
+      -> { [].join(nil) }.should complain(/warning: \$, is set to non-nil value/)
+    end
+  end
+end
+
+describe "Array#join with $," do
+  before :each do
+    @before_separator = $,
+  end
+
+  after :each do
+    suppress_warning {$, = @before_separator}
+  end
+
+  it "separates elements with default separator when the passed separator is nil" do
+    suppress_warning {
+      $, = "_"
+      [1, 2, 3].join(nil).should == '1_2_3'
+    }
+  end
+end
diff --git a/spec/ruby/core/array/keep_if_spec.rb b/spec/ruby/core/array/keep_if_spec.rb
new file mode 100644
index 0000000000..62a65a04e8
--- /dev/null
+++ b/spec/ruby/core/array/keep_if_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require_relative 'shared/keep_if'
+
+describe "Array#keep_if" do
+  it "returns the same array if no changes were made" do
+    array = [1, 2, 3]
+    array.keep_if { true }.should.equal?(array)
+  end
+
+  it_behaves_like :keep_if, :keep_if
+end
diff --git a/spec/ruby/core/array/last_spec.rb b/spec/ruby/core/array/last_spec.rb
new file mode 100644
index 0000000000..ed417bcd2a
--- /dev/null
+++ b/spec/ruby/core/array/last_spec.rb
@@ -0,0 +1,87 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#last" do
+  it "returns the last element" do
+    [1, 1, 1, 1, 2].last.should == 2
+  end
+
+  it "returns nil if self is empty" do
+    [].last.should == nil
+  end
+
+  it "returns the last count elements if given a count" do
+    [1, 2, 3, 4, 5, 9].last(3).should == [4, 5, 9]
+  end
+
+  it "returns an empty array when passed a count on an empty array" do
+    [].last(0).should == []
+    [].last(1).should == []
+  end
+
+  it "returns an empty array when count == 0" do
+    [1, 2, 3, 4, 5].last(0).should == []
+  end
+
+  it "returns an array containing the last element when passed count == 1" do
+    [1, 2, 3, 4, 5].last(1).should == [5]
+  end
+
+  it "raises an ArgumentError when count is negative" do
+    -> { [1, 2].last(-1) }.should.raise(ArgumentError)
+  end
+
+  it "returns the entire array when count > length" do
+    [1, 2, 3, 4, 5, 9].last(10).should == [1, 2, 3, 4, 5, 9]
+  end
+
+  it "returns an array which is independent to the original when passed count" do
+    ary = [1, 2, 3, 4, 5]
+    ary.last(0).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+    ary.last(1).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+    ary.last(6).replace([1,2])
+    ary.should == [1, 2, 3, 4, 5]
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    empty.last.should.equal?(empty)
+
+    array = ArraySpecs.recursive_array
+    array.last.should.equal?(array)
+  end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(2)
+    [1, 2, 3, 4, 5].last(obj).should == [4, 5]
+  end
+
+  it "raises a TypeError if the passed argument is not numeric" do
+    -> { [1,2].last(nil) }.should.raise(TypeError)
+    -> { [1,2].last("a") }.should.raise(TypeError)
+
+    obj = mock("nonnumeric")
+    -> { [1,2].last(obj) }.should.raise(TypeError)
+  end
+
+  it "does not return subclass instance on Array subclasses" do
+    ArraySpecs::MyArray[].last(0).should.instance_of?(Array)
+    ArraySpecs::MyArray[].last(2).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].last(0).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].last(1).should.instance_of?(Array)
+    ArraySpecs::MyArray[1, 2, 3].last(2).should.instance_of?(Array)
+  end
+
+  it "is not destructive" do
+    a = [1, 2, 3]
+    a.last
+    a.should == [1, 2, 3]
+    a.last(2)
+    a.should == [1, 2, 3]
+    a.last(3)
+    a.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/array/length_spec.rb b/spec/ruby/core/array/length_spec.rb
new file mode 100644
index 0000000000..e45abb2138
--- /dev/null
+++ b/spec/ruby/core/array/length_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+
+describe "Array#length" do
+  it "is an alias of Array#size" do
+    Array.instance_method(:length).should == Array.instance_method(:size)
+  end
+end
diff --git a/spec/ruby/core/array/map_spec.rb b/spec/ruby/core/array/map_spec.rb
new file mode 100644
index 0000000000..0cc394663a
--- /dev/null
+++ b/spec/ruby/core/array/map_spec.rb
@@ -0,0 +1,143 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative '../enumerable/shared/enumeratorized'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#map" do
+  it "returns a copy of array with each element replaced by the value returned by block" do
+    a = ['a', 'b', 'c', 'd']
+    b = a.map { |i| i + '!' }
+    b.should == ["a!", "b!", "c!", "d!"]
+    b.should_not.equal? a
+  end
+
+  it "does not return subclass instance" do
+    ArraySpecs::MyArray[1, 2, 3].map { |x| x + 1 }.should.instance_of?(Array)
+  end
+
+  it "does not change self" do
+    a = ['a', 'b', 'c', 'd']
+    a.map { |i| i + '!' }
+    a.should == ['a', 'b', 'c', 'd']
+  end
+
+  it "returns the evaluated value of block if it broke in the block" do
+    a = ['a', 'b', 'c', 'd']
+    b = a.map {|i|
+      if i == 'c'
+        break 0
+      else
+        i + '!'
+      end
+    }
+    b.should == 0
+  end
+
+  it "returns an Enumerator when no block given" do
+    a = [1, 2, 3]
+    a.map.should.instance_of?(Enumerator)
+  end
+
+  it "raises an ArgumentError when no block and with arguments" do
+    a = [1, 2, 3]
+    -> {
+      a.map(:foo)
+    }.should.raise(ArgumentError)
+  end
+
+  before :each do
+    @object = [1, 2, 3, 4]
+  end
+  it_behaves_like :enumeratorized_with_origin_size, :map
+
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :map
+end
+
+describe "Array#map!" do
+  it "replaces each element with the value returned by block" do
+    a = [7, 9, 3, 5]
+    a.map! { |i| i - 1 }.should.equal?(a)
+    a.should == [6, 8, 2, 4]
+  end
+
+  it "returns self" do
+    a = [1, 2, 3, 4, 5]
+    b = a.map! {|i| i+1 }
+    a.should.equal? b
+  end
+
+  it "returns the evaluated value of block but its contents is partially modified, if it broke in the block" do
+    a = ['a', 'b', 'c', 'd']
+    b = a.map! {|i|
+      if i == 'c'
+        break 0
+      else
+        i + '!'
+      end
+    }
+    b.should == 0
+    a.should == ['a!', 'b!', 'c', 'd']
+  end
+
+  it "returns an Enumerator when no block given, and the enumerator can modify the original array" do
+    a = [1, 2, 3]
+    enum = a.map!
+    enum.should.instance_of?(Enumerator)
+    enum.each{|i| "#{i}!" }
+    a.should == ["1!", "2!", "3!"]
+  end
+
+  describe "when frozen" do
+    it "raises a FrozenError" do
+      -> { ArraySpecs.frozen_array.map! {} }.should.raise(FrozenError)
+    end
+
+    it "raises a FrozenError when empty" do
+      -> { ArraySpecs.empty_frozen_array.map! {} }.should.raise(FrozenError)
+    end
+
+    it "raises a FrozenError when calling #each on the returned Enumerator" do
+      enumerator = ArraySpecs.frozen_array.map!
+      -> { enumerator.each {|x| x } }.should.raise(FrozenError)
+    end
+
+    it "raises a FrozenError when calling #each on the returned Enumerator when empty" do
+      enumerator = ArraySpecs.empty_frozen_array.map!
+      -> { enumerator.each {|x| x } }.should.raise(FrozenError)
+    end
+  end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.map! { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "only changes elements before error is raised, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.map! do |e|
+        case e
+        when 1 then -1
+        when 2 then -2
+        when 3 then raise StandardError, 'Oops'
+        else 0
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [-1, -2, 3, 4]
+  end
+
+  before :each do
+    @object = [1, 2, 3, 4]
+  end
+  it_behaves_like :enumeratorized_with_origin_size, :map!
+
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :map!
+end
diff --git a/spec/ruby/core/array/max_spec.rb b/spec/ruby/core/array/max_spec.rb
new file mode 100644
index 0000000000..868275a748
--- /dev/null
+++ b/spec/ruby/core/array/max_spec.rb
@@ -0,0 +1,116 @@
+require_relative '../../spec_helper'
+
+describe "Array#max" do
+  it "is defined on Array" do
+    [1].method(:max).owner.should.equal? Array
+  end
+
+  it "returns nil with no values" do
+    [].max.should == nil
+  end
+
+  it "returns only element in one element array" do
+    [1].max.should == 1
+  end
+
+  it "returns largest value with multiple elements" do
+    [1,2].max.should == 2
+    [2,1].max.should == 2
+  end
+
+  describe "given a block with one argument" do
+    it "yields in turn the last length-1 values from the array" do
+      ary = []
+      result = [1,2,3,4,5].max {|x| ary << x; x}
+
+      ary.should == [2,3,4,5]
+      result.should == 5
+    end
+  end
+end
+
+# From Enumerable#max, copied for better readability
+describe "Array#max" do
+  before :each do
+    @a = [2, 4, 6, 8, 10]
+
+    @e_strs = ["333", "22", "666666", "1", "55555", "1010101010"]
+    @e_ints = [333,   22,   666666,   55555, 1010101010]
+  end
+
+  it "max should return the maximum element" do
+    [18, 42].max.should == 42
+    [2, 5, 3, 6, 1, 4].max.should == 6
+  end
+
+  it "returns the maximum element (basics cases)" do
+    [55].max.should == 55
+
+    [11,99].max.should == 99
+    [99,11].max.should == 99
+    [2, 33, 4, 11].max.should == 33
+
+    [1,2,3,4,5].max.should == 5
+    [5,4,3,2,1].max.should == 5
+    [1,4,3,5,2].max.should == 5
+    [5,5,5,5,5].max.should == 5
+
+    ["aa","tt"].max.should == "tt"
+    ["tt","aa"].max.should == "tt"
+    ["2","33","4","11"].max.should == "4"
+
+    @e_strs.max.should == "666666"
+    @e_ints.max.should == 1010101010
+  end
+
+  it "returns nil for an empty Enumerable" do
+    [].max.should == nil
+  end
+
+  it "raises a NoMethodError for elements without #<=>" do
+    -> do
+      [BasicObject.new, BasicObject.new].max
+    end.should.raise(NoMethodError)
+  end
+
+  it "raises an ArgumentError for incomparable elements" do
+    -> do
+      [11,"22"].max
+    end.should.raise(ArgumentError)
+    -> do
+      [11,12,22,33].max{|a, b| nil}
+    end.should.raise(ArgumentError)
+  end
+
+  it "returns the maximum element (with block)" do
+    # with a block
+    ["2","33","4","11"].max {|a,b| a <=> b }.should == "4"
+    [ 2 , 33 , 4 , 11 ].max {|a,b| a <=> b }.should == 33
+
+    ["2","33","4","11"].max {|a,b| b <=> a }.should == "11"
+    [ 2 , 33 , 4 , 11 ].max {|a,b| b <=> a }.should == 2
+
+    @e_strs.max {|a,b| a.length <=> b.length }.should == "1010101010"
+
+    @e_strs.max {|a,b| a <=> b }.should == "666666"
+    @e_strs.max {|a,b| a.to_i <=> b.to_i }.should == "1010101010"
+
+    @e_ints.max {|a,b| a <=> b }.should == 1010101010
+    @e_ints.max {|a,b| a.to_s <=> b.to_s }.should == 666666
+  end
+
+  it "returns the minimum for enumerables that contain nils" do
+    arr = [nil, nil, true]
+    arr.max { |a, b|
+      x = a.nil? ? 1 : a ? 0 : -1
+      y = b.nil? ? 1 : b ? 0 : -1
+      x <=> y
+    }.should == nil
+  end
+
+  it "gathers whole arrays as elements when each yields multiple" do
+    multi = [[1,2], [3,4,5], [6,7,8,9]]
+    multi.max.should == [6, 7, 8, 9]
+  end
+
+end
diff --git a/spec/ruby/core/array/min_spec.rb b/spec/ruby/core/array/min_spec.rb
new file mode 100644
index 0000000000..5913e08cf8
--- /dev/null
+++ b/spec/ruby/core/array/min_spec.rb
@@ -0,0 +1,121 @@
+require_relative '../../spec_helper'
+
+describe "Array#min" do
+  it "is defined on Array" do
+    [1].method(:max).owner.should.equal? Array
+  end
+
+  it "returns nil with no values" do
+    [].min.should == nil
+  end
+
+  it "returns only element in one element array" do
+    [1].min.should == 1
+  end
+
+  it "returns smallest value with multiple elements" do
+    [1,2].min.should == 1
+    [2,1].min.should == 1
+  end
+
+  describe "given a block with one argument" do
+    it "yields in turn the last length-1 values from the array" do
+      ary = []
+      result = [1,2,3,4,5].min {|x| ary << x; x}
+
+      ary.should == [2,3,4,5]
+      result.should == 1
+    end
+  end
+end
+
+# From Enumerable#min, copied for better readability
+describe "Array#min" do
+  before :each do
+    @a = [2, 4, 6, 8, 10]
+
+    @e_strs = ["333", "22", "666666", "1", "55555", "1010101010"]
+    @e_ints = [ 333,   22,   666666,        55555,   1010101010]
+  end
+
+  it "min should return the minimum element" do
+    [18, 42].min.should == 18
+    [2, 5, 3, 6, 1, 4].min.should == 1
+  end
+
+  it "returns the minimum (basic cases)" do
+    [55].min.should == 55
+
+    [11,99].min.should ==  11
+    [99,11].min.should == 11
+    [2, 33, 4, 11].min.should == 2
+
+    [1,2,3,4,5].min.should == 1
+    [5,4,3,2,1].min.should == 1
+    [4,1,3,5,2].min.should == 1
+    [5,5,5,5,5].min.should == 5
+
+    ["aa","tt"].min.should == "aa"
+    ["tt","aa"].min.should == "aa"
+    ["2","33","4","11"].min.should == "11"
+
+    @e_strs.min.should == "1"
+    @e_ints.min.should == 22
+  end
+
+  it "returns nil for an empty Enumerable" do
+    [].min.should == nil
+  end
+
+  it "raises a NoMethodError for elements without #<=>" do
+    -> do
+      [BasicObject.new, BasicObject.new].min
+    end.should.raise(NoMethodError)
+  end
+
+  it "raises an ArgumentError for incomparable elements" do
+    -> do
+      [11,"22"].min
+    end.should.raise(ArgumentError)
+    -> do
+      [11,12,22,33].min{|a, b| nil}
+    end.should.raise(ArgumentError)
+  end
+
+  it "returns the minimum when using a block rule" do
+    ["2","33","4","11"].min {|a,b| a <=> b }.should == "11"
+    [ 2 , 33 , 4 , 11 ].min {|a,b| a <=> b }.should == 2
+
+    ["2","33","4","11"].min {|a,b| b <=> a }.should == "4"
+    [ 2 , 33 , 4 , 11 ].min {|a,b| b <=> a }.should == 33
+
+    [ 1, 2, 3, 4 ].min {|a,b| 15 }.should == 1
+
+    [11,12,22,33].min{|a, b| 2 }.should == 11
+    @i = -2
+    [11,12,22,33].min{|a, b| @i += 1 }.should == 12
+
+    @e_strs.min {|a,b| a.length <=> b.length }.should == "1"
+
+    @e_strs.min {|a,b| a <=> b }.should == "1"
+    @e_strs.min {|a,b| a.to_i <=> b.to_i }.should == "1"
+
+    @e_ints.min {|a,b| a <=> b }.should == 22
+    @e_ints.min {|a,b| a.to_s <=> b.to_s }.should == 1010101010
+  end
+
+  it "returns the minimum for enumerables that contain nils" do
+    arr = [nil, nil, true]
+    arr.min { |a, b|
+      x = a.nil? ? -1 : a ? 0 : 1
+      y = b.nil? ? -1 : b ? 0 : 1
+      x <=> y
+    }.should == nil
+  end
+
+  it "gathers whole arrays as elements when each yields multiple" do
+    multi = [[1,2], [3,4,5], [6,7,8,9]]
+    multi.min.should == [1, 2]
+  end
+
+end
diff --git a/spec/ruby/core/array/minmax_spec.rb b/spec/ruby/core/array/minmax_spec.rb
new file mode 100644
index 0000000000..e11fe63347
--- /dev/null
+++ b/spec/ruby/core/array/minmax_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/enumerable/minmax'
+
+describe "Array#minmax" do
+  before :each do
+    @enum = [6, 4, 5, 10, 8]
+    @empty_enum = []
+    @incomparable_enum = [BasicObject.new, BasicObject.new]
+    @incompatible_enum = [11, "22"]
+    @strs = ["333", "2", "60", "55555", "1010", "111"]
+  end
+
+  it_behaves_like :enumerable_minmax, :minmax
+end
diff --git a/spec/ruby/core/array/minus_spec.rb b/spec/ruby/core/array/minus_spec.rb
new file mode 100644
index 0000000000..cb1bf56d76
--- /dev/null
+++ b/spec/ruby/core/array/minus_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/difference'
+
+describe "Array#-" do
+  it_behaves_like :array_binary_difference, :-
+end
diff --git a/spec/ruby/core/array/multiply_spec.rb b/spec/ruby/core/array/multiply_spec.rb
new file mode 100644
index 0000000000..1ac14e1b09
--- /dev/null
+++ b/spec/ruby/core/array/multiply_spec.rb
@@ -0,0 +1,94 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/join'
+
+describe "Array#*" do
+  it "tries to convert the passed argument to a String using #to_str" do
+    obj = mock('separator')
+    obj.should_receive(:to_str).and_return('::')
+    ([1, 2, 3, 4] * obj).should == '1::2::3::4'
+  end
+
+  it "tires to convert the passed argument to an Integer using #to_int" do
+    obj = mock('count')
+    obj.should_receive(:to_int).and_return(2)
+    ([1, 2, 3, 4] * obj).should == [1, 2, 3, 4, 1, 2, 3, 4]
+  end
+
+  it "raises a TypeError if the argument can neither be converted to a string nor an integer" do
+    obj = mock('not a string or integer')
+    ->{ [1,2] * obj }.should.raise(TypeError)
+  end
+
+  it "converts the passed argument to a String rather than an Integer" do
+    obj = mock('2')
+    def obj.to_int() 2 end
+    def obj.to_str() "2" end
+    ([:a, :b, :c] * obj).should == "a2b2c"
+  end
+
+  it "raises a TypeError is the passed argument is nil" do
+    ->{ [1,2] * nil }.should.raise(TypeError)
+  end
+
+  it "raises an ArgumentError when passed 2 or more arguments" do
+    ->{ [1,2].send(:*, 1, 2) }.should.raise(ArgumentError)
+  end
+
+  it "raises an ArgumentError when passed no arguments" do
+    ->{ [1,2].send(:*) }.should.raise(ArgumentError)
+  end
+end
+
+describe "Array#* with an integer" do
+  it "concatenates n copies of the array when passed an integer" do
+    ([ 1, 2, 3 ] * 0).should == []
+    ([ 1, 2, 3 ] * 1).should == [1, 2, 3]
+    ([ 1, 2, 3 ] * 3).should == [1, 2, 3, 1, 2, 3, 1, 2, 3]
+    ([] * 10).should == []
+  end
+
+  it "does not return self even if the passed integer is 1" do
+    ary = [1, 2, 3]
+    (ary * 1).should_not.equal?(ary)
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    (empty * 0).should == []
+    (empty * 1).should == empty
+    (empty * 3).should == [empty, empty, empty]
+
+    array = ArraySpecs.recursive_array
+    (array * 0).should == []
+    (array * 1).should == array
+  end
+
+  it "raises an ArgumentError when passed a negative integer" do
+    -> { [ 1, 2, 3 ] * -1 }.should.raise(ArgumentError)
+    -> { [] * -1 }.should.raise(ArgumentError)
+  end
+
+  describe "with a subclass of Array" do
+    before :each do
+      ScratchPad.clear
+
+      @array = ArraySpecs::MyArray[1, 2, 3, 4, 5]
+    end
+
+    it "returns an Array instance" do
+      (@array * 0).should.instance_of?(Array)
+      (@array * 1).should.instance_of?(Array)
+      (@array * 2).should.instance_of?(Array)
+    end
+
+    it "does not call #initialize on the subclass instance" do
+      (@array * 2).should == [1, 2, 3, 4, 5, 1, 2, 3, 4, 5]
+      ScratchPad.recorded.should == nil
+    end
+  end
+end
+
+describe "Array#* with a string" do
+  it_behaves_like :array_join_with_string_separator, :*
+end
diff --git a/spec/ruby/core/array/new_spec.rb b/spec/ruby/core/array/new_spec.rb
new file mode 100644
index 0000000000..b2f23e2f6b
--- /dev/null
+++ b/spec/ruby/core/array/new_spec.rb
@@ -0,0 +1,124 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array.new" do
+  it "returns an instance of Array" do
+    Array.new.should.instance_of?(Array)
+  end
+
+  it "returns an instance of a subclass" do
+    ArraySpecs::MyArray.new(1, 2).should.instance_of?(ArraySpecs::MyArray)
+  end
+
+  it "raises an ArgumentError if passed 3 or more arguments" do
+    -> do
+      [1, 2].send :initialize, 1, 'x', true
+    end.should.raise(ArgumentError)
+    -> do
+      [1, 2].send(:initialize, 1, 'x', true) {}
+    end.should.raise(ArgumentError)
+  end
+end
+
+describe "Array.new with no arguments" do
+  it "returns an empty array" do
+    Array.new.should.empty?
+  end
+
+  it "does not use the given block" do
+    -> {
+      -> { Array.new { raise } }.should_not.raise
+    }.should complain(/warning: given block not used/, verbose: true)
+  end
+end
+
+describe "Array.new with (array)" do
+  it "returns an array initialized to the other array" do
+    b = [4, 5, 6]
+    Array.new(b).should == b
+  end
+
+  it "does not use the given block" do
+    ->{ Array.new([1, 2]) { raise } }.should_not.raise
+  end
+
+  it "calls #to_ary to convert the value to an array" do
+    a = mock("array")
+    a.should_receive(:to_ary).and_return([1, 2])
+    a.should_not_receive(:to_int)
+    Array.new(a).should == [1, 2]
+  end
+
+  it "does not call #to_ary on instances of Array or subclasses of Array" do
+    a = [1, 2]
+    a.should_not_receive(:to_ary)
+    Array.new(a)
+  end
+
+  it "raises a TypeError if an Array type argument and a default object" do
+    -> { Array.new([1, 2], 1) }.should.raise(TypeError)
+  end
+end
+
+describe "Array.new with (size, object=nil)" do
+  it "returns an array of size filled with object" do
+    obj = [3]
+    a = Array.new(2, obj)
+    a.should == [obj, obj]
+    a[0].should.equal?(obj)
+    a[1].should.equal?(obj)
+
+    Array.new(3, 14).should == [14, 14, 14]
+  end
+
+  it "returns an array of size filled with nil when object is omitted" do
+    Array.new(3).should == [nil, nil, nil]
+  end
+
+  it "raises an ArgumentError if size is negative" do
+    -> { Array.new(-1, :a) }.should.raise(ArgumentError)
+    -> { Array.new(-1) }.should.raise(ArgumentError)
+  end
+
+  it "raises an ArgumentError if size is too large" do
+    -> { Array.new(fixnum_max+1) }.should.raise(ArgumentError)
+  end
+
+  it "calls #to_int to convert the size argument to an Integer when object is given" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    Array.new(obj, :a).should == [:a]
+  end
+
+  it "calls #to_int to convert the size argument to an Integer when object is not given" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    Array.new(obj).should == [nil]
+  end
+
+  it "raises a TypeError if the size argument is not an Integer type" do
+    obj = mock('nonnumeric')
+    obj.stub!(:to_ary).and_return([1, 2])
+    ->{ Array.new(obj, :a) }.should.raise(TypeError)
+  end
+
+  it "yields the index of the element and sets the element to the value of the block" do
+    Array.new(3) { |i| i.to_s }.should == ['0', '1', '2']
+  end
+
+  it "uses the block value instead of using the default value" do
+    -> {
+      @result = Array.new(3, :obj) { |i| i.to_s }
+    }.should complain(/block supersedes default value argument/)
+    @result.should == ['0', '1', '2']
+  end
+
+  it "returns the value passed to break" do
+    a = Array.new(3) do |i|
+      break if i == 2
+      i.to_s
+    end
+
+    a.should == nil
+  end
+end
diff --git a/spec/ruby/core/array/none_spec.rb b/spec/ruby/core/array/none_spec.rb
new file mode 100644
index 0000000000..31cd8c46d6
--- /dev/null
+++ b/spec/ruby/core/array/none_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#none?" do
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :none?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].none?(/baz/) { true }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/one_spec.rb b/spec/ruby/core/array/one_spec.rb
new file mode 100644
index 0000000000..0c61907881
--- /dev/null
+++ b/spec/ruby/core/array/one_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#one?" do
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :one?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].one?(/foo/) { false }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/pack/a_spec.rb b/spec/ruby/core/array/pack/a_spec.rb
new file mode 100644
index 0000000000..03bfd8214c
--- /dev/null
+++ b/spec/ruby/core/array/pack/a_spec.rb
@@ -0,0 +1,73 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/string'
+require_relative 'shared/taint'
+
+describe "Array#pack with format 'A'" do
+  it_behaves_like :array_pack_basic, 'A'
+  it_behaves_like :array_pack_basic_non_float, 'A'
+  it_behaves_like :array_pack_no_platform, 'A'
+  it_behaves_like :array_pack_string, 'A'
+  it_behaves_like :array_pack_taint, 'A'
+
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack A string")
+    obj.should_receive(:to_str).and_return("``abcdef")
+    [obj].pack("A*").should == "``abcdef"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('A') }.should.raise(TypeError)
+    -> { [0].pack('a') }.should.raise(TypeError)
+  end
+
+  it "adds all the bytes to the output when passed the '*' modifier" do
+    ["abc"].pack("A*").should == "abc"
+  end
+
+  it "pads the output with spaces when the count exceeds the size of the String" do
+    ["abc"].pack("A6").should == "abc   "
+  end
+
+  it "adds a space when the value is nil" do
+    [nil].pack("A").should == " "
+  end
+
+  it "pads the output with spaces when the value is nil" do
+    [nil].pack("A3").should == "   "
+  end
+
+  it "does not pad with spaces when passed the '*' modifier and the value is nil" do
+    [nil].pack("A*").should == ""
+  end
+end
+
+describe "Array#pack with format 'a'" do
+  it_behaves_like :array_pack_basic, 'a'
+  it_behaves_like :array_pack_basic_non_float, 'a'
+  it_behaves_like :array_pack_no_platform, 'a'
+  it_behaves_like :array_pack_string, 'a'
+  it_behaves_like :array_pack_taint, 'a'
+
+  it "adds all the bytes to the output when passed the '*' modifier" do
+    ["abc"].pack("a*").should == "abc"
+  end
+
+  it "pads the output with NULL bytes when the count exceeds the size of the String" do
+    ["abc"].pack("a6").should == "abc\x00\x00\x00"
+  end
+
+  it "adds a NULL byte when the value is nil" do
+    [nil].pack("a").should == "\x00"
+  end
+
+  it "pads the output with NULL bytes when the value is nil" do
+    [nil].pack("a3").should == "\x00\x00\x00"
+  end
+
+  it "does not pad with NULL bytes when passed the '*' modifier and the value is nil" do
+    [nil].pack("a*").should == ""
+  end
+end
diff --git a/spec/ruby/core/array/pack/at_spec.rb b/spec/ruby/core/array/pack/at_spec.rb
new file mode 100644
index 0000000000..bb9801440a
--- /dev/null
+++ b/spec/ruby/core/array/pack/at_spec.rb
@@ -0,0 +1,30 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+
+describe "Array#pack with format '@'" do
+  it_behaves_like :array_pack_basic, '@'
+  it_behaves_like :array_pack_basic_non_float, '@'
+  it_behaves_like :array_pack_no_platform, '@'
+
+  it "moves the insertion point to the index specified by the count modifier" do
+    [1, 2, 3, 4, 5].pack("C4@2C").should == "\x01\x02\x05"
+  end
+
+  it "does not consume any elements" do
+    [1, 2, 3].pack("C@3C").should == "\x01\x00\x00\x02"
+  end
+
+  it "extends the string with NULL bytes if the string size is less than the count" do
+    [1, 2, 3].pack("@3C*").should == "\x00\x00\x00\x01\x02\x03"
+  end
+
+  it "truncates the string if the string size is greater than the count" do
+    [1, 2, 3].pack("Cx5@2C").should == "\x01\x00\x02"
+  end
+
+  it "implicitly has a count of one when no count modifier is passed" do
+    [1, 2, 3].pack("C*@").should == "\x01"
+  end
+end
diff --git a/spec/ruby/core/array/pack/b_spec.rb b/spec/ruby/core/array/pack/b_spec.rb
new file mode 100644
index 0000000000..f7576846ef
--- /dev/null
+++ b/spec/ruby/core/array/pack/b_spec.rb
@@ -0,0 +1,113 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/encodings'
+require_relative 'shared/taint'
+
+describe "Array#pack with format 'B'" do
+  it_behaves_like :array_pack_basic, 'B'
+  it_behaves_like :array_pack_basic_non_float, 'B'
+  it_behaves_like :array_pack_arguments, 'B'
+  it_behaves_like :array_pack_hex, 'B'
+  it_behaves_like :array_pack_taint, 'B'
+
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack B string")
+    obj.should_receive(:to_str).and_return("``abcdef")
+    [obj].pack("B*").should == "\x2a"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('B') }.should.raise(TypeError)
+    -> { [0].pack('b') }.should.raise(TypeError)
+  end
+
+  it "encodes one bit for each character starting with the most significant bit" do
+    [ [["0"], "\x00"],
+      [["1"], "\x80"]
+    ].should be_computed_by(:pack, "B")
+  end
+
+  it "implicitly has a count of one when not passed a count modifier" do
+    ["1"].pack("B").should == "\x80"
+  end
+
+  it "implicitly has count equal to the string length when passed the '*' modifier" do
+    [ [["00101010"], "\x2a"],
+      [["00000000"], "\x00"],
+      [["11111111"], "\xff"],
+      [["10000000"], "\x80"],
+      [["00000001"], "\x01"]
+    ].should be_computed_by(:pack, "B*")
+  end
+
+  it "encodes the least significant bit of a character other than 0 or 1" do
+    [ [["bbababab"], "\x2a"],
+      [["^&#&#^#^"], "\x2a"],
+      [["(()()()("], "\x2a"],
+      [["@@%@%@%@"], "\x2a"],
+      [["ppqrstuv"], "\x2a"],
+      [["rqtvtrqp"], "\x42"]
+    ].should be_computed_by(:pack, "B*")
+  end
+
+  it "returns a binary string" do
+    ["1"].pack("B").encoding.should == Encoding::BINARY
+  end
+
+  it "encodes the string as a sequence of bytes" do
+    ["ああああああああ"].pack("B*").should == "\xdbm\xb6"
+  end
+end
+
+describe "Array#pack with format 'b'" do
+  it_behaves_like :array_pack_basic, 'b'
+  it_behaves_like :array_pack_basic_non_float, 'b'
+  it_behaves_like :array_pack_arguments, 'b'
+  it_behaves_like :array_pack_hex, 'b'
+  it_behaves_like :array_pack_taint, 'b'
+
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack H string")
+    obj.should_receive(:to_str).and_return("`abcdef`")
+    [obj].pack("b*").should == "\x2a"
+  end
+
+  it "encodes one bit for each character starting with the least significant bit" do
+    [ [["0"], "\x00"],
+      [["1"], "\x01"]
+    ].should be_computed_by(:pack, "b")
+  end
+
+  it "implicitly has a count of one when not passed a count modifier" do
+    ["1"].pack("b").should == "\x01"
+  end
+
+  it "implicitly has count equal to the string length when passed the '*' modifier" do
+    [ [["0101010"],  "\x2a"],
+      [["00000000"], "\x00"],
+      [["11111111"], "\xff"],
+      [["10000000"], "\x01"],
+      [["00000001"], "\x80"]
+    ].should be_computed_by(:pack, "b*")
+  end
+
+  it "encodes the least significant bit of a character other than 0 or 1" do
+    [ [["bababab"], "\x2a"],
+      [["&#&#^#^"], "\x2a"],
+      [["()()()("], "\x2a"],
+      [["@%@%@%@"], "\x2a"],
+      [["pqrstuv"], "\x2a"],
+      [["qrtrtvs"], "\x41"]
+    ].should be_computed_by(:pack, "b*")
+  end
+
+  it "returns a binary string" do
+    ["1"].pack("b").encoding.should == Encoding::BINARY
+  end
+
+  it "encodes the string as a sequence of bytes" do
+    ["ああああああああ"].pack("b*").should == "\xdb\xb6m"
+  end
+end
diff --git a/spec/ruby/core/array/pack/buffer_spec.rb b/spec/ruby/core/array/pack/buffer_spec.rb
new file mode 100644
index 0000000000..d104c80186
--- /dev/null
+++ b/spec/ruby/core/array/pack/buffer_spec.rb
@@ -0,0 +1,60 @@
+# encoding: binary
+
+require_relative '../../../spec_helper'
+
+describe "Array#pack with :buffer option" do
+  it "returns specified buffer" do
+    n = [ 65, 66, 67 ]
+    buffer = " "*3
+    result = n.pack("ccc", buffer: buffer)      #=> "ABC"
+    result.should.equal?(buffer)
+  end
+
+  it "adds result at the end of buffer content" do
+    n = [ 65, 66, 67 ] # result without buffer is "ABC"
+
+    buffer = +""
+    n.pack("ccc", buffer: buffer).should == "ABC"
+
+    buffer = +"123"
+    n.pack("ccc", buffer: buffer).should == "123ABC"
+
+    buffer = +"12345"
+    n.pack("ccc", buffer: buffer).should == "12345ABC"
+  end
+
+  it "raises TypeError exception if buffer is not String" do
+    -> { [65].pack("ccc", buffer: []) }.should.raise(
+      TypeError, "buffer must be String, not Array")
+  end
+
+  it "raise FrozenError if buffer is frozen" do
+    -> { [65].pack("c", buffer: "frozen-string".freeze) }.should.raise(FrozenError)
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    [65, 66, 67].pack("ccc", buffer: buffer)
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
+  context "offset (@) is specified" do
+    it 'keeps buffer content if it is longer than offset' do
+      n = [ 65, 66, 67 ]
+      buffer = +"123456"
+      n.pack("@3ccc", buffer: buffer).should == "123ABC"
+    end
+
+    it "fills the gap with \\0 if buffer content is shorter than offset" do
+      n = [ 65, 66, 67 ]
+      buffer = +"123"
+      n.pack("@6ccc", buffer: buffer).should == "123\0\0\0ABC"
+    end
+
+    it 'does not keep buffer content if it is longer than offset + result' do
+      n = [ 65, 66, 67 ]
+      buffer = +"1234567890"
+      n.pack("@3ccc", buffer: buffer).should == "123ABC"
+    end
+  end
+end
diff --git a/spec/ruby/core/array/pack/c_spec.rb b/spec/ruby/core/array/pack/c_spec.rb
new file mode 100644
index 0000000000..de06207a23
--- /dev/null
+++ b/spec/ruby/core/array/pack/c_spec.rb
@@ -0,0 +1,77 @@
+# encoding: binary
+
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+
+describe :array_pack_8bit, shared: true do
+  it "encodes the least significant eight bits of a positive number" do
+    [ [[49],           "1"],
+      [[0b11111111],   "\xFF"],
+      [[0b100000000],  "\x00"],
+      [[0b100000001],  "\x01"]
+    ].should be_computed_by(:pack, pack_format)
+  end
+
+  it "encodes the least significant eight bits of a negative number" do
+    [ [[-1],           "\xFF"],
+      [[-0b10000000],  "\x80"],
+      [[-0b11111111],  "\x01"],
+      [[-0b100000000], "\x00"],
+      [[-0b100000001], "\xFF"]
+    ].should be_computed_by(:pack, pack_format)
+  end
+
+  it "encodes a Float truncated as an Integer" do
+    [ [[5.2], "\x05"],
+      [[5.8], "\x05"]
+    ].should be_computed_by(:pack, pack_format)
+  end
+
+  it "calls #to_int to convert the pack argument to an Integer" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(5)
+    [obj].pack(pack_format).should == "\x05"
+  end
+
+  it "encodes the number of array elements specified by the count modifier" do
+    [ [[1, 2, 3], pack_format(3), "\x01\x02\x03"],
+      [[1, 2, 3], pack_format(2) + pack_format(1), "\x01\x02\x03"]
+    ].should be_computed_by(:pack)
+  end
+
+  it "encodes all remaining elements when passed the '*' modifier" do
+    [1, 2, 3, 4, 5].pack(pack_format('*')).should == "\x01\x02\x03\x04\x05"
+  end
+
+  it "raise ArgumentError for NULL bytes between directives" do
+    -> {
+      [1, 2, 3].pack(pack_format("\000", 2))
+    }.should.raise(ArgumentError, /unknown pack directive/)
+  end
+
+  it "ignores spaces between directives" do
+    [1, 2, 3].pack(pack_format(' ', 2)).should == "\x01\x02"
+  end
+end
+
+describe "Array#pack with format 'C'" do
+  it_behaves_like :array_pack_basic, 'C'
+  it_behaves_like :array_pack_basic_non_float, 'C'
+  it_behaves_like :array_pack_8bit, 'C'
+  it_behaves_like :array_pack_arguments, 'C'
+  it_behaves_like :array_pack_numeric_basic, 'C'
+  it_behaves_like :array_pack_integer, 'C'
+  it_behaves_like :array_pack_no_platform, 'C'
+end
+
+describe "Array#pack with format 'c'" do
+  it_behaves_like :array_pack_basic, 'c'
+  it_behaves_like :array_pack_basic_non_float, 'c'
+  it_behaves_like :array_pack_8bit, 'c'
+  it_behaves_like :array_pack_arguments, 'c'
+  it_behaves_like :array_pack_numeric_basic, 'c'
+  it_behaves_like :array_pack_integer, 'c'
+  it_behaves_like :array_pack_no_platform, 'c'
+end
diff --git a/spec/ruby/core/array/pack/comment_spec.rb b/spec/ruby/core/array/pack/comment_spec.rb
new file mode 100644
index 0000000000..daf1cff06a
--- /dev/null
+++ b/spec/ruby/core/array/pack/comment_spec.rb
@@ -0,0 +1,25 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "Array#pack" do
+  it "ignores directives text from '#' to the first newline" do
+    [1, 2, 3].pack("c#this is a comment\nc").should == "\x01\x02"
+  end
+
+  it "ignores directives text from '#' to the end if no newline is present" do
+    [1, 2, 3].pack("c#this is a comment c").should == "\x01"
+  end
+
+  it "ignores comments at the start of the directives string" do
+    [1, 2, 3].pack("#this is a comment\nc").should == "\x01"
+  end
+
+  it "ignores the entire directive string if it is a comment" do
+    [1, 2, 3].pack("#this is a comment").should == ""
+  end
+
+  it "ignores multiple comments" do
+    [1, 2, 3].pack("c#comment\nc#comment\nc#c").should == "\x01\x02\x03"
+  end
+end
diff --git a/spec/ruby/core/array/pack/d_spec.rb b/spec/ruby/core/array/pack/d_spec.rb
new file mode 100644
index 0000000000..8bb3654633
--- /dev/null
+++ b/spec/ruby/core/array/pack/d_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/float'
+
+describe "Array#pack with format 'D'" do
+  it_behaves_like :array_pack_basic, 'D'
+  it_behaves_like :array_pack_basic_float, 'D'
+  it_behaves_like :array_pack_arguments, 'D'
+  it_behaves_like :array_pack_no_platform, 'D'
+  it_behaves_like :array_pack_numeric_basic, 'D'
+  it_behaves_like :array_pack_float, 'D'
+
+  little_endian do
+    it_behaves_like :array_pack_double_le, 'D'
+  end
+
+  big_endian do
+    it_behaves_like :array_pack_double_be, 'D'
+  end
+end
+
+describe "Array#pack with format 'd'" do
+  it_behaves_like :array_pack_basic, 'd'
+  it_behaves_like :array_pack_basic_float, 'd'
+  it_behaves_like :array_pack_arguments, 'd'
+  it_behaves_like :array_pack_no_platform, 'd'
+  it_behaves_like :array_pack_numeric_basic, 'd'
+  it_behaves_like :array_pack_float, 'd'
+
+  little_endian do
+    it_behaves_like :array_pack_double_le, 'd'
+  end
+
+  big_endian do
+    it_behaves_like :array_pack_double_be, 'd'
+  end
+end
diff --git a/spec/ruby/core/array/pack/e_spec.rb b/spec/ruby/core/array/pack/e_spec.rb
new file mode 100644
index 0000000000..ab61ef578f
--- /dev/null
+++ b/spec/ruby/core/array/pack/e_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/float'
+
+describe "Array#pack with format 'E'" do
+  it_behaves_like :array_pack_basic, 'E'
+  it_behaves_like :array_pack_basic_float, 'E'
+  it_behaves_like :array_pack_arguments, 'E'
+  it_behaves_like :array_pack_no_platform, 'E'
+  it_behaves_like :array_pack_numeric_basic, 'E'
+  it_behaves_like :array_pack_float, 'E'
+  it_behaves_like :array_pack_double_le, 'E'
+end
+
+describe "Array#pack with format 'e'" do
+  it_behaves_like :array_pack_basic, 'e'
+  it_behaves_like :array_pack_basic_float, 'e'
+  it_behaves_like :array_pack_arguments, 'e'
+  it_behaves_like :array_pack_no_platform, 'e'
+  it_behaves_like :array_pack_numeric_basic, 'e'
+  it_behaves_like :array_pack_float, 'e'
+  it_behaves_like :array_pack_float_le, 'e'
+end
diff --git a/spec/ruby/core/array/pack/empty_spec.rb b/spec/ruby/core/array/pack/empty_spec.rb
new file mode 100644
index 0000000000..d635d6a563
--- /dev/null
+++ b/spec/ruby/core/array/pack/empty_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+
+describe "Array#pack with empty format" do
+  it "returns an empty String" do
+    [1, 2, 3].pack("").should == ""
+  end
+
+  it "returns a String with US-ASCII encoding" do
+    [1, 2, 3].pack("").encoding.should == Encoding::US_ASCII
+  end
+end
diff --git a/spec/ruby/core/array/pack/f_spec.rb b/spec/ruby/core/array/pack/f_spec.rb
new file mode 100644
index 0000000000..d436e0787c
--- /dev/null
+++ b/spec/ruby/core/array/pack/f_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/float'
+
+describe "Array#pack with format 'F'" do
+  it_behaves_like :array_pack_basic, 'F'
+  it_behaves_like :array_pack_basic_float, 'F'
+  it_behaves_like :array_pack_arguments, 'F'
+  it_behaves_like :array_pack_no_platform, 'F'
+  it_behaves_like :array_pack_numeric_basic, 'F'
+  it_behaves_like :array_pack_float, 'F'
+
+  little_endian do
+    it_behaves_like :array_pack_float_le, 'F'
+  end
+
+  big_endian do
+    it_behaves_like :array_pack_float_be, 'F'
+  end
+end
+
+describe "Array#pack with format 'f'" do
+  it_behaves_like :array_pack_basic, 'f'
+  it_behaves_like :array_pack_basic_float, 'f'
+  it_behaves_like :array_pack_arguments, 'f'
+  it_behaves_like :array_pack_no_platform, 'f'
+  it_behaves_like :array_pack_numeric_basic, 'f'
+  it_behaves_like :array_pack_float, 'f'
+
+  little_endian do
+    it_behaves_like :array_pack_float_le, 'f'
+  end
+
+  big_endian do
+    it_behaves_like :array_pack_float_be, 'f'
+  end
+end
diff --git a/spec/ruby/core/array/pack/g_spec.rb b/spec/ruby/core/array/pack/g_spec.rb
new file mode 100644
index 0000000000..83b7f81acc
--- /dev/null
+++ b/spec/ruby/core/array/pack/g_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/float'
+
+describe "Array#pack with format 'G'" do
+  it_behaves_like :array_pack_basic, 'G'
+  it_behaves_like :array_pack_basic_float, 'G'
+  it_behaves_like :array_pack_arguments, 'G'
+  it_behaves_like :array_pack_no_platform, 'G'
+  it_behaves_like :array_pack_numeric_basic, 'G'
+  it_behaves_like :array_pack_float, 'G'
+  it_behaves_like :array_pack_double_be, 'G'
+end
+
+describe "Array#pack with format 'g'" do
+  it_behaves_like :array_pack_basic, 'g'
+  it_behaves_like :array_pack_basic_float, 'g'
+  it_behaves_like :array_pack_arguments, 'g'
+  it_behaves_like :array_pack_no_platform, 'g'
+  it_behaves_like :array_pack_numeric_basic, 'g'
+  it_behaves_like :array_pack_float, 'g'
+  it_behaves_like :array_pack_float_be, 'g'
+end
diff --git a/spec/ruby/core/array/pack/h_spec.rb b/spec/ruby/core/array/pack/h_spec.rb
new file mode 100644
index 0000000000..1492d02b1f
--- /dev/null
+++ b/spec/ruby/core/array/pack/h_spec.rb
@@ -0,0 +1,205 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/encodings'
+require_relative 'shared/taint'
+
+describe "Array#pack with format 'H'" do
+  it_behaves_like :array_pack_basic, 'H'
+  it_behaves_like :array_pack_basic_non_float, 'H'
+  it_behaves_like :array_pack_arguments, 'H'
+  it_behaves_like :array_pack_hex, 'H'
+  it_behaves_like :array_pack_taint, 'H'
+
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack H string")
+    obj.should_receive(:to_str).and_return("a")
+    [obj].pack("H").should == "\xa0"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('H') }.should.raise(TypeError)
+    -> { [0].pack('h') }.should.raise(TypeError)
+  end
+
+  it "encodes the first character as the most significant nibble when passed no count modifier" do
+    ["ab"].pack("H").should == "\xa0"
+  end
+
+  it "implicitly has count equal to the string length when passed the '*' modifier" do
+    ["deadbeef"].pack("H*").should == "\xde\xad\xbe\xef"
+  end
+
+  it "encodes count nibbles when passed a count modifier exceeding the string length" do
+    ["ab"].pack('H8').should == "\xab\x00\x00\x00"
+  end
+
+  it "encodes the first character as the most significant nibble of a hex value" do
+    [ [["0"], "\x00"],
+      [["1"], "\x10"],
+      [["2"], "\x20"],
+      [["3"], "\x30"],
+      [["4"], "\x40"],
+      [["5"], "\x50"],
+      [["6"], "\x60"],
+      [["7"], "\x70"],
+      [["8"], "\x80"],
+      [["9"], "\x90"],
+      [["a"], "\xa0"],
+      [["b"], "\xb0"],
+      [["c"], "\xc0"],
+      [["d"], "\xd0"],
+      [["e"], "\xe0"],
+      [["f"], "\xf0"],
+      [["A"], "\xa0"],
+      [["B"], "\xb0"],
+      [["C"], "\xc0"],
+      [["D"], "\xd0"],
+      [["E"], "\xe0"],
+      [["F"], "\xf0"]
+    ].should be_computed_by(:pack, "H")
+  end
+
+  it "encodes the second character as the least significant nibble of a hex value" do
+    [ [["00"], "\x00"],
+      [["01"], "\x01"],
+      [["02"], "\x02"],
+      [["03"], "\x03"],
+      [["04"], "\x04"],
+      [["05"], "\x05"],
+      [["06"], "\x06"],
+      [["07"], "\x07"],
+      [["08"], "\x08"],
+      [["09"], "\x09"],
+      [["0a"], "\x0a"],
+      [["0b"], "\x0b"],
+      [["0c"], "\x0c"],
+      [["0d"], "\x0d"],
+      [["0e"], "\x0e"],
+      [["0f"], "\x0f"],
+      [["0A"], "\x0a"],
+      [["0B"], "\x0b"],
+      [["0C"], "\x0c"],
+      [["0D"], "\x0d"],
+      [["0E"], "\x0e"],
+      [["0F"], "\x0f"]
+    ].should be_computed_by(:pack, "H2")
+  end
+
+  it "encodes the least significant nibble of a non alphanumeric character as the most significant nibble of the hex value" do
+    [ [["^"], "\xe0"],
+      [["*"], "\xa0"],
+      [["#"], "\x30"],
+      [["["], "\xb0"],
+      [["]"], "\xd0"],
+      [["@"], "\x00"],
+      [["!"], "\x10"],
+      [["H"], "\x10"],
+      [["O"], "\x80"],
+      [["T"], "\xd0"],
+      [["Z"], "\x30"],
+    ].should be_computed_by(:pack, "H")
+  end
+
+  it "returns a binary string" do
+    ["41"].pack("H").encoding.should == Encoding::BINARY
+  end
+end
+
+describe "Array#pack with format 'h'" do
+  it_behaves_like :array_pack_basic, 'h'
+  it_behaves_like :array_pack_basic_non_float, 'h'
+  it_behaves_like :array_pack_arguments, 'h'
+  it_behaves_like :array_pack_hex, 'h'
+  it_behaves_like :array_pack_taint, 'h'
+
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack H string")
+    obj.should_receive(:to_str).and_return("a")
+    [obj].pack("h").should == "\x0a"
+  end
+
+  it "encodes the first character as the least significant nibble when passed no count modifier" do
+    ["ab"].pack("h").should == "\x0a"
+  end
+
+  it "implicitly has count equal to the string length when passed the '*' modifier" do
+    ["deadbeef"].pack("h*").should == "\xed\xda\xeb\xfe"
+  end
+
+  it "encodes count nibbles when passed a count modifier exceeding the string length" do
+    ["ab"].pack('h8').should == "\xba\x00\x00\x00"
+  end
+
+  it "encodes the first character as the least significant nibble of a hex value" do
+    [ [["0"], "\x00"],
+      [["1"], "\x01"],
+      [["2"], "\x02"],
+      [["3"], "\x03"],
+      [["4"], "\x04"],
+      [["5"], "\x05"],
+      [["6"], "\x06"],
+      [["7"], "\x07"],
+      [["8"], "\x08"],
+      [["9"], "\x09"],
+      [["a"], "\x0a"],
+      [["b"], "\x0b"],
+      [["c"], "\x0c"],
+      [["d"], "\x0d"],
+      [["e"], "\x0e"],
+      [["f"], "\x0f"],
+      [["A"], "\x0a"],
+      [["B"], "\x0b"],
+      [["C"], "\x0c"],
+      [["D"], "\x0d"],
+      [["E"], "\x0e"],
+      [["F"], "\x0f"]
+    ].should be_computed_by(:pack, "h")
+  end
+
+  it "encodes the second character as the most significant nibble of a hex value" do
+    [ [["00"], "\x00"],
+      [["01"], "\x10"],
+      [["02"], "\x20"],
+      [["03"], "\x30"],
+      [["04"], "\x40"],
+      [["05"], "\x50"],
+      [["06"], "\x60"],
+      [["07"], "\x70"],
+      [["08"], "\x80"],
+      [["09"], "\x90"],
+      [["0a"], "\xa0"],
+      [["0b"], "\xb0"],
+      [["0c"], "\xc0"],
+      [["0d"], "\xd0"],
+      [["0e"], "\xe0"],
+      [["0f"], "\xf0"],
+      [["0A"], "\xa0"],
+      [["0B"], "\xb0"],
+      [["0C"], "\xc0"],
+      [["0D"], "\xd0"],
+      [["0E"], "\xe0"],
+      [["0F"], "\xf0"]
+    ].should be_computed_by(:pack, "h2")
+  end
+
+  it "encodes the least significant nibble of a non alphanumeric character as the least significant nibble of the hex value" do
+    [ [["^"], "\x0e"],
+      [["*"], "\x0a"],
+      [["#"], "\x03"],
+      [["["], "\x0b"],
+      [["]"], "\x0d"],
+      [["@"], "\x00"],
+      [["!"], "\x01"],
+      [["H"], "\x01"],
+      [["O"], "\x08"],
+      [["T"], "\x0d"],
+      [["Z"], "\x03"],
+    ].should be_computed_by(:pack, "h")
+  end
+
+  it "returns a binary string" do
+    ["41"].pack("h").encoding.should == Encoding::BINARY
+  end
+end
diff --git a/spec/ruby/core/array/pack/i_spec.rb b/spec/ruby/core/array/pack/i_spec.rb
new file mode 100644
index 0000000000..a237071227
--- /dev/null
+++ b/spec/ruby/core/array/pack/i_spec.rb
@@ -0,0 +1,133 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+describe "Array#pack with format 'I'" do
+  it_behaves_like :array_pack_basic, 'I'
+  it_behaves_like :array_pack_basic_non_float, 'I'
+  it_behaves_like :array_pack_arguments, 'I'
+  it_behaves_like :array_pack_numeric_basic, 'I'
+  it_behaves_like :array_pack_integer, 'I'
+end
+
+describe "Array#pack with format 'i'" do
+  it_behaves_like :array_pack_basic, 'i'
+  it_behaves_like :array_pack_basic_non_float, 'i'
+  it_behaves_like :array_pack_arguments, 'i'
+  it_behaves_like :array_pack_numeric_basic, 'i'
+  it_behaves_like :array_pack_integer, 'i'
+end
+
+describe "Array#pack with format 'I'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_32bit_le, 'I<'
+  end
+
+  describe "with modifier '<' and '_'" do
+    it_behaves_like :array_pack_32bit_le, 'I<_'
+    it_behaves_like :array_pack_32bit_le, 'I_<'
+  end
+
+  describe "with modifier '<' and '!'" do
+    it_behaves_like :array_pack_32bit_le, 'I<!'
+    it_behaves_like :array_pack_32bit_le, 'I!<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_32bit_be, 'I>'
+  end
+
+  describe "with modifier '>' and '_'" do
+    it_behaves_like :array_pack_32bit_be, 'I>_'
+    it_behaves_like :array_pack_32bit_be, 'I_>'
+  end
+
+  describe "with modifier '>' and '!'" do
+    it_behaves_like :array_pack_32bit_be, 'I>!'
+    it_behaves_like :array_pack_32bit_be, 'I!>'
+  end
+end
+
+describe "Array#pack with format 'i'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_32bit_le, 'i<'
+  end
+
+  describe "with modifier '<' and '_'" do
+    it_behaves_like :array_pack_32bit_le, 'i<_'
+    it_behaves_like :array_pack_32bit_le, 'i_<'
+  end
+
+  describe "with modifier '<' and '!'" do
+    it_behaves_like :array_pack_32bit_le, 'i<!'
+    it_behaves_like :array_pack_32bit_le, 'i!<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_32bit_be, 'i>'
+  end
+
+  describe "with modifier '>' and '_'" do
+    it_behaves_like :array_pack_32bit_be, 'i>_'
+    it_behaves_like :array_pack_32bit_be, 'i_>'
+  end
+
+  describe "with modifier '>' and '!'" do
+    it_behaves_like :array_pack_32bit_be, 'i>!'
+    it_behaves_like :array_pack_32bit_be, 'i!>'
+  end
+end
+
+little_endian do
+  describe "Array#pack with format 'I'" do
+    it_behaves_like :array_pack_32bit_le, 'I'
+  end
+
+  describe "Array#pack with format 'I' with modifier '_'" do
+    it_behaves_like :array_pack_32bit_le_platform, 'I_'
+  end
+
+  describe "Array#pack with format 'I' with modifier '!'" do
+    it_behaves_like :array_pack_32bit_le_platform, 'I!'
+  end
+
+  describe "Array#pack with format 'i'" do
+    it_behaves_like :array_pack_32bit_le, 'i'
+  end
+
+  describe "Array#pack with format 'i' with modifier '_'" do
+    it_behaves_like :array_pack_32bit_le_platform, 'i_'
+  end
+
+  describe "Array#pack with format 'i' with modifier '!'" do
+    it_behaves_like :array_pack_32bit_le_platform, 'i!'
+  end
+end
+
+big_endian do
+  describe "Array#pack with format 'I'" do
+    it_behaves_like :array_pack_32bit_be, 'I'
+  end
+
+  describe "Array#pack with format 'I' with modifier '_'" do
+    it_behaves_like :array_pack_32bit_be_platform, 'I_'
+  end
+
+  describe "Array#pack with format 'I' with modifier '!'" do
+    it_behaves_like :array_pack_32bit_be_platform, 'I!'
+  end
+
+  describe "Array#pack with format 'i'" do
+    it_behaves_like :array_pack_32bit_be, 'i'
+  end
+
+  describe "Array#pack with format 'i' with modifier '_'" do
+    it_behaves_like :array_pack_32bit_be_platform, 'i_'
+  end
+
+  describe "Array#pack with format 'i' with modifier '!'" do
+    it_behaves_like :array_pack_32bit_be_platform, 'i!'
+  end
+end
diff --git a/spec/ruby/core/array/pack/j_spec.rb b/spec/ruby/core/array/pack/j_spec.rb
new file mode 100644
index 0000000000..7b62d5efdf
--- /dev/null
+++ b/spec/ruby/core/array/pack/j_spec.rb
@@ -0,0 +1,217 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+platform_is pointer_size: 64 do
+  describe "Array#pack with format 'J'" do
+    it_behaves_like :array_pack_basic, 'J'
+    it_behaves_like :array_pack_basic_non_float, 'J'
+    it_behaves_like :array_pack_arguments, 'J'
+    it_behaves_like :array_pack_numeric_basic, 'J'
+    it_behaves_like :array_pack_integer, 'J'
+  end
+
+  describe "Array#pack with format 'j'" do
+    it_behaves_like :array_pack_basic, 'j'
+    it_behaves_like :array_pack_basic_non_float, 'j'
+    it_behaves_like :array_pack_arguments, 'j'
+    it_behaves_like :array_pack_numeric_basic, 'j'
+    it_behaves_like :array_pack_integer, 'j'
+  end
+
+  little_endian do
+    describe "Array#pack with format 'J'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_64bit_le, 'J_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_64bit_le, 'J!'
+      end
+    end
+
+    describe "Array#pack with format 'j'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_64bit_le, 'j_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_64bit_le, 'j!'
+      end
+    end
+  end
+
+  big_endian do
+    describe "Array#pack with format 'J'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_64bit_be, 'J_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_64bit_be, 'J!'
+      end
+    end
+
+    describe "Array#pack with format 'j'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_64bit_be, 'j_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_64bit_be, 'j!'
+      end
+    end
+  end
+
+  describe "Array#pack with format 'J'" do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_64bit_le, 'J<_'
+      it_behaves_like :array_pack_64bit_le, 'J_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_64bit_le, 'J<!'
+      it_behaves_like :array_pack_64bit_le, 'J!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_64bit_be, 'J>_'
+      it_behaves_like :array_pack_64bit_be, 'J_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_64bit_be, 'J>!'
+      it_behaves_like :array_pack_64bit_be, 'J!>'
+    end
+  end
+
+  describe "Array#pack with format 'j'" do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_64bit_le, 'j<_'
+      it_behaves_like :array_pack_64bit_le, 'j_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_64bit_le, 'j<!'
+      it_behaves_like :array_pack_64bit_le, 'j!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_64bit_be, 'j>_'
+      it_behaves_like :array_pack_64bit_be, 'j_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_64bit_be, 'j>!'
+      it_behaves_like :array_pack_64bit_be, 'j!>'
+    end
+  end
+end
+
+platform_is pointer_size: 32 do
+  describe "Array#pack with format 'J'" do
+    it_behaves_like :array_pack_basic, 'J'
+    it_behaves_like :array_pack_basic_non_float, 'J'
+    it_behaves_like :array_pack_arguments, 'J'
+    it_behaves_like :array_pack_numeric_basic, 'J'
+    it_behaves_like :array_pack_integer, 'J'
+  end
+
+  describe "Array#pack with format 'j'" do
+    it_behaves_like :array_pack_basic, 'j'
+    it_behaves_like :array_pack_basic_non_float, 'j'
+    it_behaves_like :array_pack_arguments, 'j'
+    it_behaves_like :array_pack_numeric_basic, 'j'
+    it_behaves_like :array_pack_integer, 'j'
+  end
+
+  big_endian do
+    describe "Array#pack with format 'J'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_32bit_be, 'J_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_32bit_be, 'J!'
+      end
+    end
+
+    describe "Array#pack with format 'j'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_32bit_be, 'j_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_32bit_be, 'j!'
+      end
+    end
+  end
+
+  little_endian do
+    describe "Array#pack with format 'J'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_32bit_le, 'J_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_32bit_le, 'J!'
+      end
+    end
+
+    describe "Array#pack with format 'j'" do
+      describe "with modifier '_'" do
+        it_behaves_like :array_pack_32bit_le, 'j_'
+      end
+
+      describe "with modifier '!'" do
+        it_behaves_like :array_pack_32bit_le, 'j!'
+      end
+    end
+  end
+
+  describe "Array#pack with format 'J'" do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_32bit_le, 'J<_'
+      it_behaves_like :array_pack_32bit_le, 'J_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_32bit_le, 'J<!'
+      it_behaves_like :array_pack_32bit_le, 'J!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_32bit_be, 'J>_'
+      it_behaves_like :array_pack_32bit_be, 'J_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_32bit_be, 'J>!'
+      it_behaves_like :array_pack_32bit_be, 'J!>'
+    end
+  end
+
+  describe "Array#pack with format 'j'" do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_32bit_le, 'j<_'
+      it_behaves_like :array_pack_32bit_le, 'j_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_32bit_le, 'j<!'
+      it_behaves_like :array_pack_32bit_le, 'j!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_32bit_be, 'j>_'
+      it_behaves_like :array_pack_32bit_be, 'j_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_32bit_be, 'j>!'
+      it_behaves_like :array_pack_32bit_be, 'j!>'
+    end
+  end
+end
diff --git a/spec/ruby/core/array/pack/l_spec.rb b/spec/ruby/core/array/pack/l_spec.rb
new file mode 100644
index 0000000000..f6dfb1da83
--- /dev/null
+++ b/spec/ruby/core/array/pack/l_spec.rb
@@ -0,0 +1,221 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+describe "Array#pack with format 'L'" do
+  it_behaves_like :array_pack_basic, 'L'
+  it_behaves_like :array_pack_basic_non_float, 'L'
+  it_behaves_like :array_pack_arguments, 'L'
+  it_behaves_like :array_pack_numeric_basic, 'L'
+  it_behaves_like :array_pack_integer, 'L'
+end
+
+describe "Array#pack with format 'l'" do
+  it_behaves_like :array_pack_basic, 'l'
+  it_behaves_like :array_pack_basic_non_float, 'l'
+  it_behaves_like :array_pack_arguments, 'l'
+  it_behaves_like :array_pack_numeric_basic, 'l'
+  it_behaves_like :array_pack_integer, 'l'
+end
+
+describe "Array#pack with format 'L'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_32bit_le, 'L<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_32bit_be, 'L>'
+  end
+
+  platform_is c_long_size: 32 do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_32bit_le, 'L<_'
+      it_behaves_like :array_pack_32bit_le, 'L_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_32bit_le, 'L<!'
+      it_behaves_like :array_pack_32bit_le, 'L!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_32bit_be, 'L>_'
+      it_behaves_like :array_pack_32bit_be, 'L_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_32bit_be, 'L>!'
+      it_behaves_like :array_pack_32bit_be, 'L!>'
+    end
+  end
+
+  platform_is c_long_size: 64 do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_64bit_le, 'L<_'
+      it_behaves_like :array_pack_64bit_le, 'L_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_64bit_le, 'L<!'
+      it_behaves_like :array_pack_64bit_le, 'L!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_64bit_be, 'L>_'
+      it_behaves_like :array_pack_64bit_be, 'L_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_64bit_be, 'L>!'
+      it_behaves_like :array_pack_64bit_be, 'L!>'
+    end
+  end
+end
+
+describe "Array#pack with format 'l'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_32bit_le, 'l<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_32bit_be, 'l>'
+  end
+
+  platform_is c_long_size: 32 do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_32bit_le, 'l<_'
+      it_behaves_like :array_pack_32bit_le, 'l_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_32bit_le, 'l<!'
+      it_behaves_like :array_pack_32bit_le, 'l!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_32bit_be, 'l>_'
+      it_behaves_like :array_pack_32bit_be, 'l_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_32bit_be, 'l>!'
+      it_behaves_like :array_pack_32bit_be, 'l!>'
+    end
+  end
+
+  platform_is c_long_size: 64 do
+    describe "with modifier '<' and '_'" do
+      it_behaves_like :array_pack_64bit_le, 'l<_'
+      it_behaves_like :array_pack_64bit_le, 'l_<'
+    end
+
+    describe "with modifier '<' and '!'" do
+      it_behaves_like :array_pack_64bit_le, 'l<!'
+      it_behaves_like :array_pack_64bit_le, 'l!<'
+    end
+
+    describe "with modifier '>' and '_'" do
+      it_behaves_like :array_pack_64bit_be, 'l>_'
+      it_behaves_like :array_pack_64bit_be, 'l_>'
+    end
+
+    describe "with modifier '>' and '!'" do
+      it_behaves_like :array_pack_64bit_be, 'l>!'
+      it_behaves_like :array_pack_64bit_be, 'l!>'
+    end
+  end
+end
+
+little_endian do
+  describe "Array#pack with format 'L'" do
+    it_behaves_like :array_pack_32bit_le, 'L'
+  end
+
+  describe "Array#pack with format 'l'" do
+    it_behaves_like :array_pack_32bit_le, 'l'
+  end
+
+  platform_is c_long_size: 32 do
+    describe "Array#pack with format 'L' with modifier '_'" do
+      it_behaves_like :array_pack_32bit_le, 'L_'
+    end
+
+    describe "Array#pack with format 'L' with modifier '!'" do
+      it_behaves_like :array_pack_32bit_le, 'L!'
+    end
+
+    describe "Array#pack with format 'l' with modifier '_'" do
+      it_behaves_like :array_pack_32bit_le, 'l_'
+    end
+
+    describe "Array#pack with format 'l' with modifier '!'" do
+      it_behaves_like :array_pack_32bit_le, 'l!'
+    end
+  end
+
+  platform_is c_long_size: 64 do
+    describe "Array#pack with format 'L' with modifier '_'" do
+      it_behaves_like :array_pack_64bit_le, 'L_'
+    end
+
+    describe "Array#pack with format 'L' with modifier '!'" do
+      it_behaves_like :array_pack_64bit_le, 'L!'
+    end
+
+    describe "Array#pack with format 'l' with modifier '_'" do
+      it_behaves_like :array_pack_64bit_le, 'l_'
+    end
+
+    describe "Array#pack with format 'l' with modifier '!'" do
+      it_behaves_like :array_pack_64bit_le, 'l!'
+    end
+  end
+end
+
+big_endian do
+  describe "Array#pack with format 'L'" do
+    it_behaves_like :array_pack_32bit_be, 'L'
+  end
+
+  describe "Array#pack with format 'l'" do
+    it_behaves_like :array_pack_32bit_be, 'l'
+  end
+
+  platform_is c_long_size: 32 do
+    describe "Array#pack with format 'L' with modifier '_'" do
+      it_behaves_like :array_pack_32bit_be, 'L_'
+    end
+
+    describe "Array#pack with format 'L' with modifier '!'" do
+      it_behaves_like :array_pack_32bit_be, 'L!'
+    end
+
+    describe "Array#pack with format 'l' with modifier '_'" do
+      it_behaves_like :array_pack_32bit_be, 'l_'
+    end
+
+    describe "Array#pack with format 'l' with modifier '!'" do
+      it_behaves_like :array_pack_32bit_be, 'l!'
+    end
+  end
+
+  platform_is c_long_size: 64 do
+    describe "Array#pack with format 'L' with modifier '_'" do
+      it_behaves_like :array_pack_64bit_be, 'L_'
+    end
+
+    describe "Array#pack with format 'L' with modifier '!'" do
+      it_behaves_like :array_pack_64bit_be, 'L!'
+    end
+
+    describe "Array#pack with format 'l' with modifier '_'" do
+      it_behaves_like :array_pack_64bit_be, 'l_'
+    end
+
+    describe "Array#pack with format 'l' with modifier '!'" do
+      it_behaves_like :array_pack_64bit_be, 'l!'
+    end
+  end
+end
diff --git a/spec/ruby/core/array/pack/m_spec.rb b/spec/ruby/core/array/pack/m_spec.rb
new file mode 100644
index 0000000000..fb670d120e
--- /dev/null
+++ b/spec/ruby/core/array/pack/m_spec.rb
@@ -0,0 +1,317 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/taint'
+
+describe "Array#pack with format 'M'" do
+  it_behaves_like :array_pack_basic, 'M'
+  it_behaves_like :array_pack_basic_non_float, 'M'
+  it_behaves_like :array_pack_arguments, 'M'
+  it_behaves_like :array_pack_taint, 'M'
+
+  it "encodes an empty string as an empty string" do
+    [""].pack("M").should == ""
+  end
+
+  it "encodes nil as an empty string" do
+    [nil].pack("M").should == ""
+  end
+
+  it "appends a soft line break at the end of an encoded string" do
+    ["a"].pack("M").should == "a=\n"
+  end
+
+  it "does not append a soft break if the string ends with a newline" do
+    ["a\n"].pack("M").should == "a\n"
+  end
+
+  it "encodes one element for each directive" do
+    ["a", "b", "c"].pack("MM").should == "a=\nb=\n"
+  end
+
+  it "encodes byte values 33..60 directly" do
+    [ [["!\"\#$%&'()*+,-./"], "!\"\#$%&'()*+,-./=\n"],
+      [["0123456789"],        "0123456789=\n"],
+      [[":;<"],               ":;<=\n"]
+    ].should be_computed_by(:pack, "M")
+  end
+
+  it "encodes byte values 62..126 directly" do
+    [ [[">?@"],                         ">?@=\n"],
+      [["ABCDEFGHIJKLMNOPQRSTUVWXYZ"],  "ABCDEFGHIJKLMNOPQRSTUVWXYZ=\n"],
+      [["[\\]^_`"],                     "[\\]^_`=\n"],
+      [["abcdefghijklmnopqrstuvwxyz"],  "abcdefghijklmnopqrstuvwxyz=\n"],
+      [["{|}~"],                        "{|}~=\n"]
+    ].should be_computed_by(:pack, "M")
+  end
+
+  it "encodes an '=' character in hex format" do
+    ["="].pack("M").should == "=3D=\n"
+  end
+
+  it "encodes an embedded space directly" do
+    ["a b"].pack("M").should == "a b=\n"
+  end
+
+  it "encodes a space at the end of the string directly" do
+    ["a "].pack("M").should == "a =\n"
+  end
+
+  it "encodes an embedded tab directly" do
+    ["a\tb"].pack("M").should == "a\tb=\n"
+  end
+
+  it "encodes a tab at the end of the string directly" do
+    ["a\t"].pack("M").should == "a\t=\n"
+  end
+
+  it "encodes an embedded newline directly" do
+    ["a\nb"].pack("M").should == "a\nb=\n"
+  end
+
+  it "encodes 0..31 except tab and newline in hex format" do
+    [ [["\x00\x01\x02\x03\x04\x05\x06"],  "=00=01=02=03=04=05=06=\n"],
+      [["\a\b\v\f\r"],                    "=07=08=0B=0C=0D=\n"],
+      [["\x0e\x0f\x10\x11\x12\x13\x14"],  "=0E=0F=10=11=12=13=14=\n"],
+      [["\x15\x16\x17\x18\x19\x1a"],      "=15=16=17=18=19=1A=\n"],
+      [["\e"],                            "=1B=\n"],
+      [["\x1c\x1d\x1e\x1f"],              "=1C=1D=1E=1F=\n"]
+    ].should be_computed_by(:pack, "M")
+  end
+
+  it "encodes a tab at the end of a line with an encoded newline" do
+    ["\t"].pack("M").should == "\t=\n"
+    ["\t\n"].pack("M").should == "\t=\n\n"
+    ["abc\t\nxyz"].pack("M").should == "abc\t=\n\nxyz=\n"
+  end
+
+  it "encodes a space at the end of a line with an encoded newline" do
+    [" "].pack("M").should == " =\n"
+    [" \n"].pack("M").should == " =\n\n"
+    ["abc \nxyz"].pack("M").should == "abc =\n\nxyz=\n"
+  end
+
+  it "encodes 127..255 in hex format" do
+    [ [["\x7f\x80\x81\x82\x83\x84\x85\x86"], "=7F=80=81=82=83=84=85=86=\n"],
+      [["\x87\x88\x89\x8a\x8b\x8c\x8d\x8e"], "=87=88=89=8A=8B=8C=8D=8E=\n"],
+      [["\x8f\x90\x91\x92\x93\x94\x95\x96"], "=8F=90=91=92=93=94=95=96=\n"],
+      [["\x97\x98\x99\x9a\x9b\x9c\x9d\x9e"], "=97=98=99=9A=9B=9C=9D=9E=\n"],
+      [["\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6"], "=9F=A0=A1=A2=A3=A4=A5=A6=\n"],
+      [["\xa7\xa8\xa9\xaa\xab\xac\xad\xae"], "=A7=A8=A9=AA=AB=AC=AD=AE=\n"],
+      [["\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6"], "=AF=B0=B1=B2=B3=B4=B5=B6=\n"],
+      [["\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe"], "=B7=B8=B9=BA=BB=BC=BD=BE=\n"],
+      [["\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6"], "=BF=C0=C1=C2=C3=C4=C5=C6=\n"],
+      [["\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce"], "=C7=C8=C9=CA=CB=CC=CD=CE=\n"],
+      [["\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6"], "=CF=D0=D1=D2=D3=D4=D5=D6=\n"],
+      [["\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde"], "=D7=D8=D9=DA=DB=DC=DD=DE=\n"],
+      [["\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6"], "=DF=E0=E1=E2=E3=E4=E5=E6=\n"],
+      [["\xe7\xe8\xe9\xea\xeb\xec\xed\xee"], "=E7=E8=E9=EA=EB=EC=ED=EE=\n"],
+      [["\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6"], "=EF=F0=F1=F2=F3=F4=F5=F6=\n"],
+      [["\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe"], "=F7=F8=F9=FA=FB=FC=FD=FE=\n"],
+      [["\xff"], "=FF=\n"]
+    ].should be_computed_by(:pack, "M")
+  end
+
+  it "emits a soft line break when the output exceeds 72 characters when passed '*', 0, 1, or no count modifier" do
+    s1 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+    r1 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa=\na=\n"
+    s2 = "\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19\x19"
+    r2 = "=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=19=\n=19=\n"
+    s3 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\x15a"
+    r3 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa=15=\na=\n"
+    s4 = "\x15aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\x15a"
+    r4 = "=15aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa=\na=15a=\n"
+
+    [ [[s1], "M",  r1],
+      [[s1], "M0", r1],
+      [[s1], "M1", r1],
+      [[s2], "M",  r2],
+      [[s2], "M0", r2],
+      [[s2], "M1", r2],
+      [[s3], "M",  r3],
+      [[s3], "M0", r3],
+      [[s3], "M1", r3],
+      [[s4], "M",  r4],
+      [[s4], "M0", r4],
+      [[s4], "M1", r4]
+    ].should be_computed_by(:pack)
+  end
+
+  it "emits a soft line break when the output exceeds count characters" do
+    [ [["abcdefghi"],        "M2", "abc=\ndef=\nghi=\n"],
+      [["abcdefghi"],        "M3", "abcd=\nefgh=\ni=\n"],
+      [["abcdefghi"],        "M4", "abcde=\nfghi=\n"],
+      [["abcdefghi"],        "M5", "abcdef=\nghi=\n"],
+      [["abcdefghi"],        "M6", "abcdefg=\nhi=\n"],
+      [["\x19\x19\x19\x19"], "M2", "=19=\n=19=\n=19=\n=19=\n"],
+      [["\x19\x19\x19\x19"], "M3", "=19=19=\n=19=19=\n"],
+      [["\x19\x19\x19\x19"], "M4", "=19=19=\n=19=19=\n"],
+      [["\x19\x19\x19\x19"], "M5", "=19=19=\n=19=19=\n"],
+      [["\x19\x19\x19\x19"], "M6", "=19=19=19=\n=19=\n"],
+      [["\x19\x19\x19\x19"], "M7", "=19=19=19=\n=19=\n"]
+    ].should be_computed_by(:pack)
+  end
+
+  it "encodes a recursive array" do
+    empty = ArraySpecs.empty_recursive_array
+    empty.pack('M').should.instance_of?(String)
+
+    array = ArraySpecs.recursive_array
+    array.pack('M').should == "1=\n"
+  end
+
+  it "calls #to_s to convert an object to a String" do
+    obj = mock("pack M string")
+    obj.should_receive(:to_s).and_return("packing")
+
+    [obj].pack("M").should == "packing=\n"
+  end
+
+  it "converts the object to a String representation if #to_s does not return a String" do
+    obj = mock("pack M non-string")
+    obj.should_receive(:to_s).and_return(2)
+
+    [obj].pack("M").should.instance_of?(String)
+  end
+
+  it "encodes a Symbol as a String" do
+    [:symbol].pack("M").should == "symbol=\n"
+  end
+
+  it "encodes an Integer as a String" do
+    [ [[1],             "1=\n"],
+      [[bignum_value],  "#{bignum_value}=\n"]
+    ].should be_computed_by(:pack, "M")
+  end
+
+  it "encodes a Float as a String" do
+    [1.0].pack("M").should == "1.0=\n"
+  end
+
+  it "converts Floats to the minimum unique representation" do
+    [1.0 / 3.0].pack("M").should == "0.3333333333333333=\n"
+  end
+
+  it "sets the output string to US-ASCII encoding" do
+    ["abcd"].pack("M").encoding.should == Encoding::US_ASCII
+  end
+end
+
+describe "Array#pack with format 'm'" do
+  it_behaves_like :array_pack_basic, 'm'
+  it_behaves_like :array_pack_basic_non_float, 'm'
+  it_behaves_like :array_pack_arguments, 'm'
+  it_behaves_like :array_pack_taint, 'm'
+
+  it "encodes an empty string as an empty string" do
+    [""].pack("m").should == ""
+  end
+
+  it "appends a newline to the end of the encoded string" do
+    ["a"].pack("m").should == "YQ==\n"
+  end
+
+  it "encodes one element per directive" do
+    ["abc", "DEF"].pack("mm").should == "YWJj\nREVG\n"
+  end
+
+  it "encodes 1, 2, or 3 characters in 4 output characters (Base64 encoding)" do
+    [ [["a"],       "YQ==\n"],
+      [["ab"],      "YWI=\n"],
+      [["abc"],     "YWJj\n"],
+      [["abcd"],    "YWJjZA==\n"],
+      [["abcde"],   "YWJjZGU=\n"],
+      [["abcdef"],  "YWJjZGVm\n"],
+      [["abcdefg"], "YWJjZGVmZw==\n"],
+    ].should be_computed_by(:pack, "m")
+  end
+
+  it "emits a newline after complete groups of count / 3 input characters when passed a count modifier" do
+    ["abcdefg"].pack("m3").should == "YWJj\nZGVm\nZw==\n"
+  end
+
+  it "implicitly has a count of 45 when passed '*', 1, 2 or no count modifier" do
+    s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+    r = "YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh\nYWFhYWE=\n"
+    [ [[s], "m", r],
+      [[s], "m*", r],
+      [[s], "m1", r],
+      [[s], "m2", r],
+    ].should be_computed_by(:pack)
+  end
+
+  it "encodes all ascii characters" do
+    [ [["\x00\x01\x02\x03\x04\x05\x06"],          "AAECAwQFBg==\n"],
+      [["\a\b\t\n\v\f\r"],                        "BwgJCgsMDQ==\n"],
+      [["\x0E\x0F\x10\x11\x12\x13\x14\x15\x16"],  "Dg8QERITFBUW\n"],
+      [["\x17\x18\x19\x1a\e\x1c\x1d\x1e\x1f"],    "FxgZGhscHR4f\n"],
+      [["!\"\#$%&'()*+,-./"],                     "ISIjJCUmJygpKissLS4v\n"],
+      [["0123456789"],                            "MDEyMzQ1Njc4OQ==\n"],
+      [[":;<=>?@"],                               "Ojs8PT4/QA==\n"],
+      [["ABCDEFGHIJKLMNOPQRSTUVWXYZ"],            "QUJDREVGR0hJSktMTU5PUFFSU1RVVldYWVo=\n"],
+      [["[\\]^_`"],                               "W1xdXl9g\n"],
+      [["abcdefghijklmnopqrstuvwxyz"],            "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXo=\n"],
+      [["{|}~"],                                  "e3x9fg==\n"],
+      [["\x7f\xc2\x80\xc2\x81\xc2\x82\xc2\x83"],  "f8KAwoHCgsKD\n"],
+      [["\xc2\x84\xc2\x85\xc2\x86\xc2\x87\xc2"],  "woTChcKGwofC\n"],
+      [["\x88\xc2\x89\xc2\x8a\xc2\x8b\xc2\x8c"],  "iMKJworCi8KM\n"],
+      [["\xc2\x8d\xc2\x8e\xc2\x8f\xc2\x90\xc2"],  "wo3CjsKPwpDC\n"],
+      [["\x91\xc2\x92\xc2\x93\xc2\x94\xc2\x95"],  "kcKSwpPClMKV\n"],
+      [["\xc2\x96\xc2\x97\xc2\x98\xc2\x99\xc2"],  "wpbCl8KYwpnC\n"],
+      [["\x9a\xc2\x9b\xc2\x9c\xc2\x9d\xc2\x9e"],  "msKbwpzCncKe\n"],
+      [["\xc2\x9f\xc2\xa0\xc2\xa1\xc2\xa2\xc2"],  "wp/CoMKhwqLC\n"],
+      [["\xa3\xc2\xa4\xc2\xa5\xc2\xa6\xc2\xa7"],  "o8KkwqXCpsKn\n"],
+      [["\xc2\xa8\xc2\xa9\xc2\xaa\xc2\xab\xc2"],  "wqjCqcKqwqvC\n"],
+      [["\xac\xc2\xad\xc2\xae\xc2\xaf\xc2\xb0"],  "rMKtwq7Cr8Kw\n"],
+      [["\xc2\xb1\xc2\xb2\xc2\xb3\xc2\xb4\xc2"],  "wrHCssKzwrTC\n"],
+      [["\xb5\xc2\xb6\xc2\xb7\xc2\xb8\xc2\xb9"],  "tcK2wrfCuMK5\n"],
+      [["\xc2\xba\xc2\xbb\xc2\xbc\xc2\xbd\xc2"],  "wrrCu8K8wr3C\n"],
+      [["\xbe\xc2\xbf\xc3\x80\xc3\x81\xc3\x82"],  "vsK/w4DDgcOC\n"],
+      [["\xc3\x83\xc3\x84\xc3\x85\xc3\x86\xc3"],  "w4PDhMOFw4bD\n"],
+      [["\x87\xc3\x88\xc3\x89\xc3\x8a\xc3\x8b"],  "h8OIw4nDisOL\n"],
+      [["\xc3\x8c\xc3\x8d\xc3\x8e\xc3\x8f\xc3"],  "w4zDjcOOw4/D\n"],
+      [["\x90\xc3\x91\xc3\x92\xc3\x93\xc3\x94"],  "kMORw5LDk8OU\n"],
+      [["\xc3\x95\xc3\x96\xc3\x97\xc3\x98\xc3"],  "w5XDlsOXw5jD\n"],
+      [["\x99\xc3\x9a\xc3\x9b\xc3\x9c\xc3\x9d"],  "mcOaw5vDnMOd\n"],
+      [["\xc3\x9e\xc3\x9f\xc3\xa0\xc3\xa1\xc3"],  "w57Dn8Ogw6HD\n"],
+      [["\xa2\xc3\xa3\xc3\xa4\xc3\xa5\xc3\xa6"],  "osOjw6TDpcOm\n"],
+      [["\xc3\xa7\xc3\xa8\xc3\xa9\xc3\xaa\xc3"],  "w6fDqMOpw6rD\n"],
+      [["\xab\xc3\xac\xc3\xad\xc3\xae\xc3\xaf"],  "q8Osw63DrsOv\n"],
+      [["\xc3\xb0\xc3\xb1\xc3\xb2\xc3\xb3\xc3"],  "w7DDscOyw7PD\n"],
+      [["\xb4\xc3\xb5\xc3\xb6\xc3\xb7\xc3\xb8"],  "tMO1w7bDt8O4\n"],
+      [["\xc3\xb9\xc3\xba\xc3\xbb\xc3\xbc\xc3"],  "w7nDusO7w7zD\n"],
+      [["\xbd\xc3\xbe\xc3\xbf"],                  "vcO+w78=\n"]
+    ].should be_computed_by(:pack, "m")
+  end
+
+  it "calls #to_str to convert an object to a String" do
+    obj = mock("pack m string")
+    obj.should_receive(:to_str).and_return("abc")
+    [obj].pack("m").should == "YWJj\n"
+  end
+
+  it "raises a TypeError if #to_str does not return a String" do
+    obj = mock("pack m non-string")
+    -> { [obj].pack("m") }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed nil" do
+    -> { [nil].pack("m") }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if passed an Integer" do
+    -> { [0].pack("m") }.should.raise(TypeError)
+    -> { [bignum_value].pack("m") }.should.raise(TypeError)
+  end
+
+  it "does not emit a newline if passed zero as the count modifier" do
+    s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+    r = "YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWE="
+    [s].pack("m0").should == r
+  end
+
+  it "sets the output string to US-ASCII encoding" do
+    ["abcd"].pack("m").encoding.should == Encoding::US_ASCII
+  end
+end
diff --git a/spec/ruby/core/array/pack/n_spec.rb b/spec/ruby/core/array/pack/n_spec.rb
new file mode 100644
index 0000000000..ab9409fc1e
--- /dev/null
+++ b/spec/ruby/core/array/pack/n_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+describe "Array#pack with format 'N'" do
+  it_behaves_like :array_pack_basic, 'N'
+  it_behaves_like :array_pack_basic_non_float, 'N'
+  it_behaves_like :array_pack_arguments, 'N'
+  it_behaves_like :array_pack_numeric_basic, 'N'
+  it_behaves_like :array_pack_integer, 'N'
+  it_behaves_like :array_pack_no_platform, 'N'
+  it_behaves_like :array_pack_32bit_be, 'N'
+end
+
+describe "Array#pack with format 'n'" do
+  it_behaves_like :array_pack_basic, 'n'
+  it_behaves_like :array_pack_basic_non_float, 'n'
+  it_behaves_like :array_pack_arguments, 'n'
+  it_behaves_like :array_pack_numeric_basic, 'n'
+  it_behaves_like :array_pack_integer, 'n'
+  it_behaves_like :array_pack_no_platform, 'n'
+  it_behaves_like :array_pack_16bit_be, 'n'
+end
diff --git a/spec/ruby/core/array/pack/p_spec.rb b/spec/ruby/core/array/pack/p_spec.rb
new file mode 100644
index 0000000000..b023bf9110
--- /dev/null
+++ b/spec/ruby/core/array/pack/p_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/taint'
+
+describe "Array#pack with format 'P'" do
+  it_behaves_like :array_pack_basic_non_float, 'P'
+  it_behaves_like :array_pack_taint, 'P'
+
+  it "produces as many bytes as there are in a pointer" do
+    ["hello"].pack("P").size.should == [0].pack("J").size
+  end
+
+  it "round-trips a string through pack and unpack" do
+    ["hello"].pack("P").unpack("P5").should == ["hello"]
+  end
+
+  it "with nil gives a null pointer" do
+    [nil].pack("P").unpack("J").should == [0]
+  end
+end
+
+describe "Array#pack with format 'p'" do
+  it_behaves_like :array_pack_basic_non_float, 'p'
+  it_behaves_like :array_pack_taint, 'p'
+
+  it "produces as many bytes as there are in a pointer" do
+    ["hello"].pack("p").size.should == [0].pack("J").size
+  end
+
+  it "round-trips a string through pack and unpack" do
+    ["hello"].pack("p").unpack("p").should == ["hello"]
+  end
+
+  it "with nil gives a null pointer" do
+    [nil].pack("p").unpack("J").should == [0]
+  end
+end
diff --git a/spec/ruby/core/array/pack/percent_spec.rb b/spec/ruby/core/array/pack/percent_spec.rb
new file mode 100644
index 0000000000..29b119732a
--- /dev/null
+++ b/spec/ruby/core/array/pack/percent_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+
+describe "Array#pack with format '%'" do
+  it "raises an Argument Error" do
+    -> { [1].pack("%") }.should.raise(ArgumentError)
+  end
+end
diff --git a/spec/ruby/core/array/pack/q_spec.rb b/spec/ruby/core/array/pack/q_spec.rb
new file mode 100644
index 0000000000..bd6b2a4b71
--- /dev/null
+++ b/spec/ruby/core/array/pack/q_spec.rb
@@ -0,0 +1,61 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+describe "Array#pack with format 'Q'" do
+  it_behaves_like :array_pack_basic, 'Q'
+  it_behaves_like :array_pack_basic_non_float, 'Q'
+  it_behaves_like :array_pack_arguments, 'Q'
+  it_behaves_like :array_pack_numeric_basic, 'Q'
+  it_behaves_like :array_pack_integer, 'Q'
+end
+
+describe "Array#pack with format 'q'" do
+  it_behaves_like :array_pack_basic, 'q'
+  it_behaves_like :array_pack_basic_non_float, 'q'
+  it_behaves_like :array_pack_arguments, 'q'
+  it_behaves_like :array_pack_numeric_basic, 'q'
+  it_behaves_like :array_pack_integer, 'q'
+end
+
+describe "Array#pack with format 'Q'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_64bit_le, 'Q<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_64bit_be, 'Q>'
+  end
+end
+
+describe "Array#pack with format 'q'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_64bit_le, 'q<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_64bit_be, 'q>'
+  end
+end
+
+little_endian do
+  describe "Array#pack with format 'Q'" do
+    it_behaves_like :array_pack_64bit_le, 'Q'
+  end
+
+  describe "Array#pack with format 'q'" do
+    it_behaves_like :array_pack_64bit_le, 'q'
+  end
+end
+
+big_endian do
+  describe "Array#pack with format 'Q'" do
+    it_behaves_like :array_pack_64bit_be, 'Q'
+  end
+
+  describe "Array#pack with format 'q'" do
+    it_behaves_like :array_pack_64bit_be, 'q'
+  end
+end
diff --git a/spec/ruby/core/array/pack/r_spec.rb b/spec/ruby/core/array/pack/r_spec.rb
new file mode 100644
index 0000000000..cefe1388d2
--- /dev/null
+++ b/spec/ruby/core/array/pack/r_spec.rb
@@ -0,0 +1,89 @@
+# encoding: binary
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+ruby_version_is "4.1" do
+  describe "Array#pack with format 'R'" do
+    it_behaves_like :array_pack_basic, 'R'
+    it_behaves_like :array_pack_basic_non_float, 'R'
+    it_behaves_like :array_pack_arguments, 'R'
+    it_behaves_like :array_pack_numeric_basic, 'R'
+    it_behaves_like :array_pack_integer, 'R'
+
+    it "encodes a ULEB128 integer" do
+      [ [[0],            "\x00"],
+        [[1],            "\x01"],
+        [[127],          "\x7f"],
+        [[128],          "\x80\x01"],
+        [[0x3fff],       "\xff\x7f"],
+        [[0x4000],       "\x80\x80\x01"],
+        [[0xffffffff],   "\xff\xff\xff\xff\x0f"],
+        [[0x100000000],  "\x80\x80\x80\x80\x10"],
+        [[0xffff_ffff_ffff_ffff], "\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01"],
+        [[0xffff_ffff_ffff_ffff_ffff_ffff], "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x1f"],
+      ].should be_computed_by(:pack, "R")
+    end
+
+    it "encodes multiple values with '*' modifier" do
+      [1, 2].pack("R*").should == "\x01\x02"
+      [127, 128].pack("R*").should == "\x7f\x80\x01"
+    end
+
+    it "raises an ArgumentError when passed a negative value" do
+      -> { [-1].pack("R") }.should.raise(ArgumentError)
+      -> { [-100].pack("R") }.should.raise(ArgumentError)
+    end
+
+    it "round-trips values through pack and unpack" do
+      values = [0, 1, 127, 128, 0x3fff, 0x4000, 0xffffffff, 0x100000000]
+      values.pack("R*").unpack("R*").should == values
+    end
+  end
+
+  describe "Array#pack with format 'r'" do
+    it_behaves_like :array_pack_basic, 'r'
+    it_behaves_like :array_pack_basic_non_float, 'r'
+    it_behaves_like :array_pack_arguments, 'r'
+    it_behaves_like :array_pack_numeric_basic, 'r'
+    it_behaves_like :array_pack_integer, 'r'
+
+    it "encodes a SLEB128 integer" do
+      [ [[0],     "\x00"],
+        [[1],     "\x01"],
+        [[-1],    "\x7f"],
+        [[-2],    "\x7e"],
+        [[127],   "\xff\x00"],
+        [[128],   "\x80\x01"],
+        [[-127],  "\x81\x7f"],
+        [[-128],  "\x80\x7f"],
+      ].should be_computed_by(:pack, "r")
+    end
+
+    it "encodes larger positive numbers" do
+      [0x3fff].pack("r").should == "\xff\xff\x00"
+      [0x4000].pack("r").should == "\x80\x80\x01"
+    end
+
+    it "encodes larger negative numbers" do
+      [-0x3fff].pack("r").should == "\x81\x80\x7f"
+      [-0x4000].pack("r").should == "\x80\x80\x7f"
+    end
+
+    it "encodes very large numbers" do
+      [0xffff_ffff_ffff_ffff_ffff_ffff].pack("r").should == "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x1F"
+      [-0xffff_ffff_ffff_ffff_ffff_ffff].pack("r").should == "\x81\x80\x80\x80\x80\x80\x80\x80\x80\x80\x80\x80\x80\x60"
+    end
+
+    it "encodes multiple values with '*' modifier" do
+      [0, 1, -1].pack("r*").should == "\x00\x01\x7f"
+    end
+
+    it "round-trips values through pack and unpack" do
+      values = [0, 1, -1, 127, -127, 128, -128, 0x3fff, -0x3fff, 0x4000, -0x4000]
+      values.pack("r*").unpack("r*").should == values
+    end
+  end
+end
diff --git a/spec/ruby/core/array/pack/s_spec.rb b/spec/ruby/core/array/pack/s_spec.rb
new file mode 100644
index 0000000000..4212d6a0b1
--- /dev/null
+++ b/spec/ruby/core/array/pack/s_spec.rb
@@ -0,0 +1,133 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+require_relative 'shared/basic'
+require_relative 'shared/numeric_basic'
+require_relative 'shared/integer'
+
+describe "Array#pack with format 'S'" do
+  it_behaves_like :array_pack_basic, 'S'
+  it_behaves_like :array_pack_basic_non_float, 'S'
+  it_behaves_like :array_pack_arguments, 'S'
+  it_behaves_like :array_pack_numeric_basic, 'S'
+  it_behaves_like :array_pack_integer, 'S'
+end
+
+describe "Array#pack with format 's'" do
+  it_behaves_like :array_pack_basic, 's'
+  it_behaves_like :array_pack_basic_non_float, 's'
+  it_behaves_like :array_pack_arguments, 's'
+  it_behaves_like :array_pack_numeric_basic, 's'
+  it_behaves_like :array_pack_integer, 's'
+end
+
+describe "Array#pack with format 'S'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_16bit_le, 'S<'
+  end
+
+  describe "with modifier '<' and '_'" do
+    it_behaves_like :array_pack_16bit_le, 'S<_'
+    it_behaves_like :array_pack_16bit_le, 'S_<'
+  end
+
+  describe "with modifier '<' and '!'" do
+    it_behaves_like :array_pack_16bit_le, 'S<!'
+    it_behaves_like :array_pack_16bit_le, 'S!<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_16bit_be, 'S>'
+  end
+
+  describe "with modifier '>' and '_'" do
+    it_behaves_like :array_pack_16bit_be, 'S>_'
+    it_behaves_like :array_pack_16bit_be, 'S_>'
+  end
+
+  describe "with modifier '>' and '!'" do
+    it_behaves_like :array_pack_16bit_be, 'S>!'
+    it_behaves_like :array_pack_16bit_be, 'S!>'
+  end
+end
+
+describe "Array#pack with format 's'" do
+  describe "with modifier '<'" do
+    it_behaves_like :array_pack_16bit_le, 's<'
+  end
+
+  describe "with modifier '<' and '_'" do
+    it_behaves_like :array_pack_16bit_le, 's<_'
+    it_behaves_like :array_pack_16bit_le, 's_<'
+  end
+
+  describe "with modifier '<' and '!'" do
+    it_behaves_like :array_pack_16bit_le, 's<!'
+    it_behaves_like :array_pack_16bit_le, 's!<'
+  end
+
+  describe "with modifier '>'" do
+    it_behaves_like :array_pack_16bit_be, 's>'
+  end
+
+  describe "with modifier '>' and '_'" do
+    it_behaves_like :array_pack_16bit_be, 's>_'
+    it_behaves_like :array_pack_16bit_be, 's_>'
+  end
+
+  describe "with modifier '>' and '!'" do
+    it_behaves_like :array_pack_16bit_be, 's>!'
+    it_behaves_like :array_pack_16bit_be, 's!>'
+  end
+end
+
+little_endian do
+  describe "Array#pack with format 'S'" do
+    it_behaves_like :array_pack_16bit_le, 'S'
+  end
+
+  describe "Array#pack with format 'S' with modifier '_'" do
+    it_behaves_like :array_pack_16bit_le, 'S_'
+  end
+
+  describe "Array#pack with format 'S' with modifier '!'" do
+    it_behaves_like :array_pack_16bit_le, 'S!'
+  end
+
+  describe "Array#pack with format 's'" do
+    it_behaves_like :array_pack_16bit_le, 's'
+  end
+
+  describe "Array#pack with format 's' with modifier '_'" do
+    it_behaves_like :array_pack_16bit_le, 's_'
+  end
+
+  describe "Array#pack with format 's' with modifier '!'" do
+    it_behaves_like :array_pack_16bit_le, 's!'
+  end
+end
+
+big_endian do
+  describe "Array#pack with format 'S'" do
+    it_behaves_like :array_pack_16bit_be, 'S'
+  end
+
+  describe "Array#pack with format 'S' with modifier '_'" do
+    it_behaves_like :array_pack_16bit_be, 'S_'
+  end
+
+  describe "Array#pack with format 'S' with modifier '!'" do
+    it_behaves_like :array_pack_16bit_be, 'S!'
+  end
+
+  describe "Array#pack with format 's'" do
+    it_behaves_like :array_pack_16bit_be, 's'
+  end
+
+  describe "Array#pack with format 's' with modifier '_'" do
+    it_behaves_like :array_pack_16bit_be, 's_'
+  end
+
+  describe "Array#pack with format 's' with modifier '!'" do
+    it_behaves_like :array_pack_16bit_be, 's!'
+  end
+end
diff --git a/spec/ruby/core/array/pack/shared/basic.rb b/spec/ruby/core/array/pack/shared/basic.rb
new file mode 100644
index 0000000000..2894369c71
--- /dev/null
+++ b/spec/ruby/core/array/pack/shared/basic.rb
@@ -0,0 +1,73 @@
+describe :array_pack_arguments, shared: true do
+  it "raises an ArgumentError if there are fewer elements than the format requires" do
+    -> { [].pack(pack_format(1)) }.should.raise(ArgumentError)
+  end
+end
+
+describe :array_pack_basic, shared: true do
+  before :each do
+    @obj = ArraySpecs.universal_pack_object
+  end
+
+  it "raises a TypeError when passed nil" do
+    -> { [@obj].pack(nil) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError when passed an Integer" do
+    -> { [@obj].pack(1) }.should.raise(TypeError)
+  end
+end
+
+describe :array_pack_basic_non_float, shared: true do
+  before :each do
+    @obj = ArraySpecs.universal_pack_object
+  end
+
+  it "ignores whitespace in the format string" do
+    [@obj, @obj].pack("a \t\n\v\f\r"+pack_format).should.instance_of?(String)
+  end
+
+  it "ignores comments in the format string" do
+    # 2 additional directives ('a') are required for the X directive
+    [@obj, @obj, @obj, @obj].pack("aa #{pack_format} # some comment \n#{pack_format}").should.instance_of?(String)
+  end
+
+  it "raise ArgumentError when a directive is unknown" do
+    # additional directive ('a') is required for the X directive
+    -> { [@obj, @obj].pack("a K" + pack_format) }.should.raise(ArgumentError, /unknown pack directive 'K'/)
+    -> { [@obj, @obj].pack("a 0" + pack_format) }.should.raise(ArgumentError, /unknown pack directive '0'/)
+    -> { [@obj, @obj].pack("a :" + pack_format) }.should.raise(ArgumentError, /unknown pack directive ':'/)
+  end
+
+  it "calls #to_str to coerce the directives string" do
+    d = mock("pack directive")
+    d.should_receive(:to_str).and_return("x"+pack_format)
+    [@obj, @obj].pack(d).should.instance_of?(String)
+  end
+end
+
+describe :array_pack_basic_float, shared: true do
+  it "ignores whitespace in the format string" do
+    [9.3, 4.7].pack(" \t\n\v\f\r"+pack_format).should.instance_of?(String)
+  end
+
+  it "ignores comments in the format string" do
+    [9.3, 4.7].pack(pack_format + "# some comment \n" + pack_format).should.instance_of?(String)
+  end
+
+  it "calls #to_str to coerce the directives string" do
+    d = mock("pack directive")
+    d.should_receive(:to_str).and_return("x"+pack_format)
+    [1.2, 4.7].pack(d).should.instance_of?(String)
+  end
+end
+
+describe :array_pack_no_platform, shared: true do
+  it "raises ArgumentError when the format modifier is '_'" do
+    ->{ [1].pack(pack_format("_")) }.should.raise(ArgumentError)
+  end
+
+  it "raises ArgumentError when the format modifier is '!'" do
+    ->{ [1].pack(pack_format("!")) }.should.raise(ArgumentError)
+  end
+end
diff --git a/spec/ruby/core/array/pack/shared/encodings.rb b/spec/ruby/core/array/pack/shared/encodings.rb
new file mode 100644
index 0000000000..0b5a5cc8a0
--- /dev/null
+++ b/spec/ruby/core/array/pack/shared/encodings.rb
@@ -0,0 +1,16 @@
+describe :array_pack_hex, shared: true do
+  it "encodes no bytes when passed zero as the count modifier" do
+    ["abc"].pack(pack_format(0)).should == ""
+  end
+
+  it "raises a TypeError if the object does not respond to #to_str" do
+    obj = mock("pack hex non-string")
+    -> { [obj].pack(pack_format) }.should.raise(TypeError)
+  end
+
+  it "raises a TypeError if #to_str does not return a String" do
+    obj = mock("pack hex non-string")
+    obj.should_receive(:to_str).and_return(1)
+    -> { [obj].pack(pack_format) }.should.raise(TypeError)
+  end
+end
diff --git a/spec/ruby/core/array/pack/shared/float.rb b/spec/ruby/core/array/pack/shared/float.rb
new file mode 100644
index 0000000000..c1efcd7677
--- /dev/null
+++ b/spec/ruby/core/array/pack/shared/float.rb
@@ -0,0 +1,255 @@
+# encoding: binary
+
+describe :array_pack_float_le, shared: true do
+  it "encodes a positive Float" do
+    [1.42].pack(pack_format).should == "\x8f\xc2\xb5?"
+  end
+
+  it "encodes a negative Float" do
+    [-34.2].pack(pack_format).should == "\xcd\xcc\x08\xc2"
+  end
+
+  it "converts an Integer to a Float" do
+    [8].pack(pack_format).should == "\x00\x00\x00A"
+  end
+
+  it "raises a TypeError if passed a String representation of a floating point number" do
+    -> { ["13"].pack(pack_format) }.should.raise(TypeError)
+  end
+
+  it "encodes the number of array elements specified by the count modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format(nil, 2)).should == "\x9a\x999@33\xb3?"
+  end
+
+  it "encodes all remaining elements when passed the '*' modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format("*")).should == "\x9a\x999@33\xb3?33\x03A"
+  end
+
+  it "raise ArgumentError for NULL bytes between directives" do
+    -> {
+      [5.3, 9.2].pack(pack_format("\000", 2))
+    }.should.raise(ArgumentError, /unknown pack directive/)
+  end
+
+  it "ignores spaces between directives" do
+    [5.3, 9.2].pack(pack_format(" ", 2)).should == "\x9a\x99\xa9@33\x13A"
+  end
+
+  it "encodes positive Infinity" do
+    [infinity_value].pack(pack_format).should == "\x00\x00\x80\x7f"
+  end
+
+  it "encodes negative Infinity" do
+    [-infinity_value].pack(pack_format).should == "\x00\x00\x80\xff"
+  end
+
+  it "encodes NaN" do
+    nans = ["\x00\x00\xc0\xff", "\x00\x00\xc0\x7f", "\xFF\xFF\xFF\x7F"]
+    nans.should.include?([nan_value].pack(pack_format))
+  end
+
+  it "encodes a positive Float outside the range of a single precision float" do
+    [1e150].pack(pack_format).should == "\x00\x00\x80\x7f"
+  end
+
+  it "encodes a negative Float outside the range of a single precision float" do
+    [-1e150].pack(pack_format).should == "\x00\x00\x80\xff"
+  end
+
+  it "encodes a bignum as a float" do
+    [2 ** 65].pack(pack_format).should == [(2 ** 65).to_f].pack(pack_format)
+  end
+
+  it "encodes a rational as a float" do
+    [Rational(3, 4)].pack(pack_format).should == [Rational(3, 4).to_f].pack(pack_format)
+  end
+end
+
+describe :array_pack_float_be, shared: true do
+  it "encodes a positive Float" do
+    [1.42].pack(pack_format).should == "?\xb5\xc2\x8f"
+  end
+
+  it "encodes a negative Float" do
+    [-34.2].pack(pack_format).should == "\xc2\x08\xcc\xcd"
+  end
+
+  it "converts an Integer to a Float" do
+    [8].pack(pack_format).should == "A\x00\x00\x00"
+    [bignum_value].pack(pack_format).should == "_\x80\x00\x00"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "A\x00\x00\x00"
+  end
+
+  it "raises a TypeError if passed a String representation of a floating point number" do
+    -> { ["13"].pack(pack_format) }.should.raise(TypeError)
+  end
+
+  it "encodes the number of array elements specified by the count modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format(nil, 2)).should == "@9\x99\x9a?\xb333"
+  end
+
+  it "encodes all remaining elements when passed the '*' modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@9\x99\x9a?\xb333A\x0333"
+  end
+
+  it "raise ArgumentError for NULL bytes between directives" do
+    -> {
+      [5.3, 9.2].pack(pack_format("\000", 2))
+    }.should.raise(ArgumentError, /unknown pack directive/)
+  end
+
+  it "ignores spaces between directives" do
+    [5.3, 9.2].pack(pack_format(" ", 2)).should == "@\xa9\x99\x9aA\x1333"
+  end
+
+  it "encodes positive Infinity" do
+    [infinity_value].pack(pack_format).should == "\x7f\x80\x00\x00"
+  end
+
+  it "encodes negative Infinity" do
+    [-infinity_value].pack(pack_format).should == "\xff\x80\x00\x00"
+  end
+
+  it "encodes NaN" do
+    nans = ["\xff\xc0\x00\x00", "\x7f\xc0\x00\x00", "\x7F\xFF\xFF\xFF"]
+    nans.should.include?([nan_value].pack(pack_format))
+  end
+
+  it "encodes a positive Float outside the range of a single precision float" do
+    [1e150].pack(pack_format).should == "\x7f\x80\x00\x00"
+  end
+
+  it "encodes a negative Float outside the range of a single precision float" do
+    [-1e150].pack(pack_format).should == "\xff\x80\x00\x00"
+  end
+end
+
+describe :array_pack_double_le, shared: true do
+  it "encodes a positive Float" do
+    [1.42].pack(pack_format).should == "\xb8\x1e\x85\xebQ\xb8\xf6?"
+  end
+
+  it "encodes a negative Float" do
+    [-34.2].pack(pack_format).should == "\x9a\x99\x99\x99\x99\x19A\xc0"
+  end
+
+  it "converts an Integer to a Float" do
+    [8].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\x20@"
+    [bignum_value].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\xF0C"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00 @"
+  end
+
+  it "raises a TypeError if passed a String representation of a floating point number" do
+    -> { ["13"].pack(pack_format) }.should.raise(TypeError)
+  end
+
+  it "encodes the number of array elements specified by the count modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format(nil, 2)).should == "333333\x07@ffffff\xf6?"
+  end
+
+  it "encodes all remaining elements when passed the '*' modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format("*")).should == "333333\x07@ffffff\xf6?ffffff\x20@"
+  end
+
+  it "raise ArgumentError for NULL bytes between directives" do
+    -> {
+      [5.3, 9.2].pack(pack_format("\000", 2))
+    }.should.raise(ArgumentError, /unknown pack directive/)
+  end
+
+  it "ignores spaces between directives" do
+    [5.3, 9.2].pack(pack_format(" ", 2)).should == "333333\x15@ffffff\x22@"
+  end
+
+  it "encodes positive Infinity" do
+    [infinity_value].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\xf0\x7f"
+  end
+
+  it "encodes negative Infinity" do
+    [-infinity_value].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\xf0\xff"
+  end
+
+  it "encodes NaN" do
+    nans = [
+      "\x00\x00\x00\x00\x00\x00\xf8\xff",
+      "\x00\x00\x00\x00\x00\x00\xf8\x7f",
+      "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x7F"
+    ]
+    nans.should.include?([nan_value].pack(pack_format))
+  end
+
+  it "encodes a positive Float outside the range of a single precision float" do
+    [1e150].pack(pack_format).should == "\xaf\x96P\x2e5\x8d\x13_"
+  end
+
+  it "encodes a negative Float outside the range of a single precision float" do
+    [-1e150].pack(pack_format).should == "\xaf\x96P\x2e5\x8d\x13\xdf"
+  end
+end
+
+describe :array_pack_double_be, shared: true do
+  it "encodes a positive Float" do
+    [1.42].pack(pack_format).should == "?\xf6\xb8Q\xeb\x85\x1e\xb8"
+  end
+
+  it "encodes a negative Float" do
+    [-34.2].pack(pack_format).should == "\xc0A\x19\x99\x99\x99\x99\x9a"
+  end
+
+  it "converts an Integer to a Float" do
+    [8].pack(pack_format).should == "@\x20\x00\x00\x00\x00\x00\x00"
+  end
+
+  it "raises a TypeError if passed a String representation of a floating point number" do
+    -> { ["13"].pack(pack_format) }.should.raise(TypeError)
+  end
+
+  it "encodes the number of array elements specified by the count modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format(nil, 2)).should == "@\x07333333?\xf6ffffff"
+  end
+
+  it "encodes all remaining elements when passed the '*' modifier" do
+    [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@\x07333333?\xf6ffffff@\x20ffffff"
+  end
+
+  it "raise ArgumentError for NULL bytes between directives" do
+    -> {
+      [5.3, 9.2].pack(pack_format("\000", 2))
+    }.should.raise(ArgumentError, /unknown pack directive/)
+  end
+
+  it "ignores spaces between directives" do
+    [5.3, 9.2].pack(pack_format(" ", 2)).should == "@\x15333333@\x22ffffff"
+  end
+
+  it "encodes positive Infinity" do
+    [infinity_value].pack(pack_format).should == "\x7f\xf0\x00\x00\x00\x00\x00\x00"
+  end
+
+  it "encodes negative Infinity" do
+    [-infinity_value].pack(pack_format).should == "\xff\xf0\x00\x00\x00\x00\x00\x00"
+  end
+
+  it "encodes NaN" do
+    nans = [
+      "\xff\xf8\x00\x00\x00\x00\x00\x00",
+      "\x7f\xf8\x00\x00\x00\x00\x00\x00",
+      "\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
+    ]
+    nans.should.include?([nan_value].pack(pack_format))
+  end
+
+  it "encodes a positive Float outside the range of a single precision float" do
+    [1e150].pack(pack_format).should == "_\x13\x8d5\x2eP\x96\xaf"
+  end
+
+  it "encodes a negative Float outside the range of a single precision float" do
+    [-1e150].pack(pack_format).should == "\xdf\x13\x8d5\x2eP\x96\xaf"
+  end
+end
diff --git a/spec/ruby/core/array/pack/shared/integer.rb b/spec/ruby/core/array/pack/shared/integer.rb
new file mode 100644