116 files changed, 2515 insertions, 0 deletions
diff --git a/spec/ruby/library/set/add_spec.rb b/spec/ruby/library/set/add_spec.rb
new file mode 100644
index 0000000000..68356cc111
--- /dev/null
+++ b/spec/ruby/library/set/add_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/add'
+
+describe "Set#add" do
+  it_behaves_like :set_add, :add
+end
+
+describe "Set#add?" do
+  before :each do
+    @set = Set.new
+  end
+
+  it "adds the passed Object to self" do
+    @set.add?("cat")
+    @set.should include("cat")
+  end
+
+  it "returns self when the Object has not yet been added to self" do
+    @set.add?("cat").should equal(@set)
+  end
+
+  it "returns nil when the Object has already been added to self" do
+    @set.add?("cat")
+    @set.add?("cat").should be_nil
+  end
+end
diff --git a/spec/ruby/library/set/append_spec.rb b/spec/ruby/library/set/append_spec.rb
new file mode 100644
index 0000000000..8b3498b779
--- /dev/null
+++ b/spec/ruby/library/set/append_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/add'
+
+describe "Set#<<" do
+  it_behaves_like :set_add, :<<
+end
diff --git a/spec/ruby/library/set/case_compare_spec.rb b/spec/ruby/library/set/case_compare_spec.rb
new file mode 100644
index 0000000000..70d392a27d
--- /dev/null
+++ b/spec/ruby/library/set/case_compare_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+require 'set'
+
+describe "Set#===" do
+  it_behaves_like :set_include, :===
+
+  it "is an alias for include?" do
+    set = Set.new
+    set.method(:===).should == set.method(:include?)
+  end
+end
diff --git a/spec/ruby/library/set/case_equality_spec.rb b/spec/ruby/library/set/case_equality_spec.rb
new file mode 100644
index 0000000000..10cbfd380a
--- /dev/null
+++ b/spec/ruby/library/set/case_equality_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+require 'set'
+
+describe "Set#===" do
+  it_behaves_like :set_include, :===
+end
diff --git a/spec/ruby/library/set/classify_spec.rb b/spec/ruby/library/set/classify_spec.rb
new file mode 100644
index 0000000000..ec600c91d6
--- /dev/null
+++ b/spec/ruby/library/set/classify_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#classify" do
+  before :each do
+    @set = Set["one", "two", "three", "four"]
+  end
+
+  it "yields each Object in self" do
+    res = []
+    @set.classify { |x| res << x }
+    res.sort.should == ["one", "two", "three", "four"].sort
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.classify
+    enum.should be_an_instance_of(Enumerator)
+
+    classified = enum.each { |x| x.length }
+    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
+  end
+
+  it "classifies the Objects in self based on the block's return value" do
+    classified = @set.classify { |x| x.length }
+    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
+  end
+end
diff --git a/spec/ruby/library/set/clear_spec.rb b/spec/ruby/library/set/clear_spec.rb
new file mode 100644
index 0000000000..2b1c9c5b5a
--- /dev/null
+++ b/spec/ruby/library/set/clear_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#clear" do
+  before :each do
+    @set = Set["one", "two", "three", "four"]
+  end
+
+  it "removes all elements from self" do
+    @set.clear
+    @set.should be_empty
+  end
+
+  it "returns self" do
+    @set.clear.should equal(@set)
+  end
+end
diff --git a/spec/ruby/library/set/collect_spec.rb b/spec/ruby/library/set/collect_spec.rb
new file mode 100644
index 0000000000..f8813a9331
--- /dev/null
+++ b/spec/ruby/library/set/collect_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/collect'
+
+describe "Set#collect!" do
+  it_behaves_like :set_collect_bang, :collect!
+end
diff --git a/spec/ruby/library/set/compare_by_identity_spec.rb b/spec/ruby/library/set/compare_by_identity_spec.rb
new file mode 100644
index 0000000000..9ed1602189
--- /dev/null
+++ b/spec/ruby/library/set/compare_by_identity_spec.rb
@@ -0,0 +1,143 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#compare_by_identity" do
+  it "compares its members by identity" do
+    a = "a"
+    b1 = "b"
+    b2 = "b"
+
+    set = Set.new
+    set.compare_by_identity
+    set.merge([a, a, b1, b2])
+    set.to_a.sort.should == [a, b1, b2].sort
+  end
+
+  it "causes future comparisons on the receiver to be made by identity" do
+    elt = [1]
+    set = Set.new
+    set << elt
+    set.member?(elt.dup).should be_true
+    set.compare_by_identity
+    set.member?(elt.dup).should be_false
+  end
+
+  it "rehashes internally so that old members can be looked up" do
+    set = Set.new
+    (1..10).each { |k| set << k }
+    o = Object.new
+    def o.hash; 123; end
+    set << o
+    set.compare_by_identity
+    set.member?(o).should be_true
+  end
+
+  it "returns self" do
+    set = Set.new
+    result = set.compare_by_identity
+    result.should equal(set)
+  end
+
+  it "is idempotent and has no effect on an already compare_by_identity set" do
+    set = Set.new.compare_by_identity
+    set << :foo
+    set.compare_by_identity.should equal(set)
+    set.should.compare_by_identity?
+    set.to_a.should == [:foo]
+  end
+
+  it "uses the semantics of BasicObject#equal? to determine members identity" do
+    :a.equal?(:a).should == true
+    Set.new.compare_by_identity.merge([:a, :a]).to_a.should == [:a]
+
+    ary1 = [1]
+    ary2 = [1]
+    ary1.equal?(ary2).should == false
+    Set.new.compare_by_identity.merge([ary1, ary2]).to_a.sort.should == [ary1, ary2].sort
+  end
+
+  it "uses #equal? semantics, but doesn't actually call #equal? to determine identity" do
+    set = Set.new.compare_by_identity
+    obj = mock("equal")
+    obj.should_not_receive(:equal?)
+    set << :foo
+    set << obj
+    set.to_a.should == [:foo, obj]
+  end
+
+  it "does not call #hash on members" do
+    elt = mock("element")
+    elt.should_not_receive(:hash)
+    set = Set.new.compare_by_identity
+    set << elt
+    set.member?(elt).should be_true
+  end
+
+  it "regards #dup'd objects as having different identities" do
+    a1 = "a"
+    a2 = a1.dup
+
+    set = Set.new.compare_by_identity
+    set.merge([a1, a2])
+    set.to_a.sort.should == [a1, a2].sort
+  end
+
+  it "regards #clone'd objects as having different identities" do
+    a1 = "a"
+    a2 = a1.clone
+
+    set = Set.new.compare_by_identity
+    set.merge([a1, a2])
+    set.to_a.sort.should == [a1, a2].sort
+  end
+
+  it "raises a FrozenError on frozen sets" do
+    set = Set.new.freeze
+    -> {
+      set.compare_by_identity
+    }.should raise_error(FrozenError, /frozen Hash/)
+  end
+
+  it "persists over #dups" do
+    set = Set.new.compare_by_identity
+    set << :a
+    set_dup = set.dup
+    set_dup.should == set
+    set_dup << :a
+    set_dup.to_a.should == [:a]
+  end
+
+  it "persists over #clones" do
+    set = Set.new.compare_by_identity
+    set << :a
+    set_clone = set.clone
+    set_clone.should == set
+    set_clone << :a
+    set_clone.to_a.should == [:a]
+  end
+
+  it "is not equal to set what does not compare by identity" do
+    Set.new([1, 2]).should == Set.new([1, 2])
+    Set.new([1, 2]).should_not == Set.new([1, 2]).compare_by_identity
+  end
+end
+
+describe "Set#compare_by_identity?" do
+  it "returns false by default" do
+    Set.new.should_not.compare_by_identity?
+  end
+
+  it "returns true once #compare_by_identity has been invoked on self" do
+    set = Set.new
+    set.compare_by_identity
+    set.should.compare_by_identity?
+  end
+
+  it "returns true when called multiple times on the same set" do
+    set = Set.new
+    set.compare_by_identity
+    set.should.compare_by_identity?
+    set.should.compare_by_identity?
+    set.should.compare_by_identity?
+  end
+end
diff --git a/spec/ruby/library/set/comparison_spec.rb b/spec/ruby/library/set/comparison_spec.rb
new file mode 100644
index 0000000000..b851ea3d57
--- /dev/null
+++ b/spec/ruby/library/set/comparison_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../spec_helper'
+require 'set'
+
+ruby_version_is "3.0" do
+  describe "Set#<=>" do
+    it "returns 0 if the sets are equal" do
+      (Set[] <=> Set[]).should == 0
+      (Set[:a, :b, :c] <=> Set[:a, :b, :c]).should == 0
+    end
+
+    it "returns -1 if the set is a proper subset of the other set" do
+      (Set[] <=> Set[1]).should == -1
+      (Set[1, 2] <=> Set[1, 2, 3]).should == -1
+    end
+
+    it "returns +1 if the set is a proper superset of other set" do
+      (Set[1] <=> Set[]).should == +1
+      (Set[1, 2, 3] <=> Set[1, 2]).should == +1
+    end
+
+    it "returns nil if the set has unique elements" do
+      (Set[1, 2, 3] <=> Set[:a, :b, :c]).should be_nil
+    end
+
+    it "returns nil when the argument is not set-like" do
+      (Set[] <=> false).should be_nil
+    end
+  end
+end
diff --git a/spec/ruby/library/set/constructor_spec.rb b/spec/ruby/library/set/constructor_spec.rb
new file mode 100644
index 0000000000..bb84861514
--- /dev/null
+++ b/spec/ruby/library/set/constructor_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set[]" do
+  it "returns a new Set populated with the passed Objects" do
+    set = Set[1, 2, 3]
+
+    set.instance_of?(Set).should be_true
+    set.size.should eql(3)
+
+    set.should include(1)
+    set.should include(2)
+    set.should include(3)
+  end
+end
diff --git a/spec/ruby/library/set/delete_if_spec.rb b/spec/ruby/library/set/delete_if_spec.rb
new file mode 100644
index 0000000000..33caeeaab7
--- /dev/null
+++ b/spec/ruby/library/set/delete_if_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#delete_if" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.delete_if { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "deletes every element from self for which the passed block returns true" do
+    @set.delete_if { |x| x.size == 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self" do
+    @set.delete_if { |x| x }.should equal(@set)
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.delete_if
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size == 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/library/set/delete_spec.rb b/spec/ruby/library/set/delete_spec.rb
new file mode 100644
index 0000000000..b12524384a
--- /dev/null
+++ b/spec/ruby/library/set/delete_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#delete" do
+  before :each do
+    @set = Set["a", "b", "c"]
+  end
+
+  it "deletes the passed Object from self" do
+    @set.delete("a")
+    @set.should_not include("a")
+  end
+
+  it "returns self" do
+    @set.delete("a").should equal(@set)
+    @set.delete("x").should equal(@set)
+  end
+end
+
+describe "Set#delete?" do
+  before :each do
+    @set = Set["a", "b", "c"]
+  end
+
+  it "deletes the passed Object from self" do
+    @set.delete?("a")
+    @set.should_not include("a")
+  end
+
+  it "returns self when the passed Object is in self" do
+    @set.delete?("a").should equal(@set)
+  end
+
+  it "returns nil when the passed Object is not in self" do
+    @set.delete?("x").should be_nil
+  end
+end
diff --git a/spec/ruby/library/set/difference_spec.rb b/spec/ruby/library/set/difference_spec.rb
new file mode 100644
index 0000000000..422f2ed3c7
--- /dev/null
+++ b/spec/ruby/library/set/difference_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/difference'
+
+describe "Set#difference" do
+  it_behaves_like :set_difference, :difference
+end
diff --git a/spec/ruby/library/set/disjoint_spec.rb b/spec/ruby/library/set/disjoint_spec.rb
new file mode 100644
index 0000000000..ea3b141455
--- /dev/null
+++ b/spec/ruby/library/set/disjoint_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#disjoint?" do
+  it "returns false when two Sets have at least one element in common" do
+    Set[1, 2].disjoint?(Set[2, 3]).should == false
+  end
+
+  it "returns true when two Sets have no element in common" do
+    Set[1, 2].disjoint?(Set[3, 4]).should == true
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns false when a Set has at least one element in common with a Set-like object" do
+      Set[1, 2].disjoint?(SetSpecs::SetLike.new([2, 3])).should be_false
+    end
+
+    it "returns true when a Set has no element in common with a Set-like object" do
+      Set[1, 2].disjoint?(SetSpecs::SetLike.new([3, 4])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/set/divide_spec.rb b/spec/ruby/library/set/divide_spec.rb
new file mode 100644
index 0000000000..fdd8cd9622
--- /dev/null
+++ b/spec/ruby/library/set/divide_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#divide" do
+  it "divides self into a set of subsets based on the blocks return values" do
+    set = Set["one", "two", "three", "four", "five"].divide { |x| x.length }
+    set.map { |x| x.to_a.sort }.sort.should == [["five", "four"], ["one", "two"], ["three"]]
+  end
+
+  it "yields each Object to the block" do
+    ret = []
+    Set["one", "two", "three", "four", "five"].divide { |x| ret << x }
+    ret.sort.should == ["five", "four", "one", "three", "two"]
+  end
+
+  # BUG: Does not raise a LocalJumpError, but a NoMethodError
+  #
+  # it "raises a LocalJumpError when not passed a block" do
+  #   lambda { Set[1].divide }.should raise_error(LocalJumpError)
+  # end
+end
+
+describe "Set#divide when passed a block with an arity of 2" do
+  it "divides self into a set of subsets based on the blocks return values" do
+    set = Set[1, 3, 4, 6, 9, 10, 11].divide { |x, y| (x - y).abs == 1 }
+    set.map{ |x| x.to_a.sort }.sort.should == [[1], [3, 4], [6], [9, 10, 11]]
+  end
+
+  it "yields each two Object to the block" do
+    ret = []
+    Set[1, 2].divide { |x, y| ret << [x, y] }
+    ret.sort.should == [[1, 1], [1, 2], [2, 1], [2, 2]]
+  end
+end
diff --git a/spec/ruby/library/set/each_spec.rb b/spec/ruby/library/set/each_spec.rb
new file mode 100644
index 0000000000..9bb5ead03a
--- /dev/null
+++ b/spec/ruby/library/set/each_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#each" do
+  before :each do
+    @set = Set[1, 2, 3]
+  end
+
+  it "yields each Object in self" do
+    ret = []
+    @set.each { |x| ret << x }
+    ret.sort.should == [1, 2, 3]
+  end
+
+  it "returns self" do
+    @set.each { |x| x }.should equal(@set)
+  end
+
+  it "returns an Enumerator when not passed a block" do
+    enum = @set.each
+
+    ret = []
+    enum.each { |x| ret << x }
+    ret.sort.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/library/set/empty_spec.rb b/spec/ruby/library/set/empty_spec.rb
new file mode 100644
index 0000000000..1789a664c7
--- /dev/null
+++ b/spec/ruby/library/set/empty_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#empty?" do
+  it "returns true if self is empty" do
+    Set[].empty?.should be_true
+    Set[1].empty?.should be_false
+    Set[1,2,3].empty?.should be_false
+  end
+end
diff --git a/spec/ruby/library/set/enumerable/to_set_spec.rb b/spec/ruby/library/set/enumerable/to_set_spec.rb
new file mode 100644
index 0000000000..3790d8deee
--- /dev/null
+++ b/spec/ruby/library/set/enumerable/to_set_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'set'
+
+describe "Enumerable#to_set" do
+  it "returns a new Set created from self" do
+    [1, 2, 3].to_set.should == Set[1, 2, 3]
+    {a: 1, b: 2}.to_set.should == Set[[:b, 2], [:a, 1]]
+  end
+
+  ruby_version_is ''...'3.0' do
+    it "allows passing an alternate class for Set" do
+      sorted_set = [1, 2, 3].to_set(SortedSet)
+      sorted_set.should == SortedSet[1, 2, 3]
+      sorted_set.instance_of?(SortedSet).should == true
+    end
+  end
+
+  it "passes down passed blocks" do
+    [1, 2, 3].to_set { |x| x * x }.should == Set[1, 4, 9]
+  end
+end
diff --git a/spec/ruby/library/set/eql_spec.rb b/spec/ruby/library/set/eql_spec.rb
new file mode 100644
index 0000000000..dd8e633775
--- /dev/null
+++ b/spec/ruby/library/set/eql_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#eql?" do
+  it "returns true when the passed argument is a Set and contains the same elements" do
+    Set[].should eql(Set[])
+    Set[1, 2, 3].should eql(Set[1, 2, 3])
+    Set[1, 2, 3].should eql(Set[3, 2, 1])
+    Set["a", :b, ?c].should eql(Set[?c, :b, "a"])
+
+    Set[1, 2, 3].should_not eql(Set[1.0, 2, 3])
+    Set[1, 2, 3].should_not eql(Set[2, 3])
+    Set[1, 2, 3].should_not eql(Set[])
+  end
+end
diff --git a/spec/ruby/library/set/equal_value_spec.rb b/spec/ruby/library/set/equal_value_spec.rb
new file mode 100644
index 0000000000..f5b5f790c0
--- /dev/null
+++ b/spec/ruby/library/set/equal_value_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#==" do
+  it "returns true when the passed Object is a Set and self and the Object contain the same elements" do
+    Set[].should == Set[]
+    Set[1, 2, 3].should == Set[1, 2, 3]
+    Set["1", "2", "3"].should == Set["1", "2", "3"]
+
+    Set[1, 2, 3].should_not == Set[1.0, 2, 3]
+    Set[1, 2, 3].should_not == [1, 2, 3]
+  end
+
+  it "does not depend on the order of the elements" do
+    Set[1, 2, 3].should == Set[3, 2, 1]
+    Set[:a, "b", ?c].should == Set[?c, "b", :a]
+  end
+
+  it "does not depend on the order of nested Sets" do
+    Set[Set[1], Set[2], Set[3]].should == Set[Set[3], Set[2], Set[1]]
+
+    set1 = Set[Set["a", "b"], Set["c", "d"], Set["e", "f"]]
+    set2 = Set[Set["c", "d"], Set["a", "b"], Set["e", "f"]]
+    set1.should == set2
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true when a Set and a Set-like object contain the same elements" do
+      Set[1, 2, 3].should == SetSpecs::SetLike.new([1, 2, 3])
+    end
+  end
+end
diff --git a/spec/ruby/library/set/exclusion_spec.rb b/spec/ruby/library/set/exclusion_spec.rb
new file mode 100644
index 0000000000..5bc4b5a2bf
--- /dev/null
+++ b/spec/ruby/library/set/exclusion_spec.rb
@@ -0,0 +1,18 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#^" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns a new Set containing elements that are not in both self and the passed Enumerable" do
+    (@set ^ Set[3, 4, 5]).should == Set[1, 2, 5]
+    (@set ^ [3, 4, 5]).should == Set[1, 2, 5]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set ^ 3 }.should raise_error(ArgumentError)
+    -> { @set ^ Object.new }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/filter_spec.rb b/spec/ruby/library/set/filter_spec.rb
new file mode 100644
index 0000000000..779254ad68
--- /dev/null
+++ b/spec/ruby/library/set/filter_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/select'
+
+describe "Set#filter!" do
+  it_behaves_like :set_select_bang, :filter!
+end
diff --git a/spec/ruby/library/set/fixtures/set_like.rb b/spec/ruby/library/set/fixtures/set_like.rb
new file mode 100644
index 0000000000..46f61a451e
--- /dev/null
+++ b/spec/ruby/library/set/fixtures/set_like.rb
@@ -0,0 +1,31 @@
+require 'set'
+
+module SetSpecs
+  # This class is used to test the interaction of "Set-like" objects with real Sets
+  #
+  # These "Set-like" objects reply to is_a?(Set) with true and thus real Set objects are able to transparently
+  # interoperate with them in a duck-typing manner.
+  class SetLike
+    include Enumerable
+
+    def is_a?(klass)
+      super || klass == ::Set
+    end
+
+    def initialize(entries)
+      @entries = entries
+    end
+
+    def each(&block)
+      @entries.each(&block)
+    end
+
+    def inspect
+      "#<#{self.class}: {#{map(&:inspect).join(", ")}}>"
+    end
+
+    def size
+      @entries.size
+    end
+  end
+end
diff --git a/spec/ruby/library/set/flatten_merge_spec.rb b/spec/ruby/library/set/flatten_merge_spec.rb
new file mode 100644
index 0000000000..f2c99a9481
--- /dev/null
+++ b/spec/ruby/library/set/flatten_merge_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#flatten_merge" do
+  it "is protected" do
+    Set.should have_protected_instance_method("flatten_merge")
+  end
+
+  it "flattens the passed Set and merges it into self" do
+    set1 = Set[1, 2]
+    set2 = Set[3, 4, Set[5, 6]]
+
+    set1.send(:flatten_merge, set2).should == Set[1, 2, 3, 4, 5, 6]
+  end
+
+  it "raises an ArgumentError when trying to flatten a recursive Set" do
+    set1 = Set[1, 2, 3]
+    set2 = Set[5, 6, 7]
+    set2 << set2
+
+    -> { set1.send(:flatten_merge, set2) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/flatten_spec.rb b/spec/ruby/library/set/flatten_spec.rb
new file mode 100644
index 0000000000..4ac83ea825
--- /dev/null
+++ b/spec/ruby/library/set/flatten_spec.rb
@@ -0,0 +1,53 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#flatten" do
+  it "returns a copy of self with each included Set flattened" do
+    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
+    flattened_set = set.flatten
+
+    flattened_set.should_not equal(set)
+    flattened_set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+  end
+
+  it "raises an ArgumentError when self is recursive" do
+    (set = Set[]) << set
+    -> { set.flatten }.should raise_error(ArgumentError)
+  end
+
+  context "when Set contains a Set-like object" do
+    it "returns a copy of self with each included Set-like object flattened" do
+      Set[SetSpecs::SetLike.new([1])].flatten.should == Set[1]
+    end
+  end
+end
+
+describe "Set#flatten!" do
+  it "flattens self" do
+    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
+    set.flatten!
+    set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+  end
+
+  it "returns self when self was modified" do
+    set = Set[1, 2, Set[3, 4]]
+    set.flatten!.should equal(set)
+  end
+
+  it "returns nil when self was not modified" do
+    set = Set[1, 2, 3, 4]
+    set.flatten!.should be_nil
+  end
+
+  it "raises an ArgumentError when self is recursive" do
+    (set = Set[]) << set
+    -> { set.flatten! }.should raise_error(ArgumentError)
+  end
+
+  context "when Set contains a Set-like object" do
+    it "flattens self, including Set-like objects" do
+      Set[SetSpecs::SetLike.new([1])].flatten!.should == Set[1]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/hash_spec.rb b/spec/ruby/library/set/hash_spec.rb
new file mode 100644
index 0000000000..47c43c05f1
--- /dev/null
+++ b/spec/ruby/library/set/hash_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#hash" do
+  it "is static" do
+    Set[].hash.should == Set[].hash
+    Set[1, 2, 3].hash.should == Set[1, 2, 3].hash
+    Set[:a, "b", ?c].hash.should == Set[?c, "b", :a].hash
+
+    Set[].hash.should_not == Set[1, 2, 3].hash
+    Set[1, 2, 3].hash.should_not == Set[:a, "b", ?c].hash
+  end
+end
diff --git a/spec/ruby/library/set/include_spec.rb b/spec/ruby/library/set/include_spec.rb
new file mode 100644
index 0000000000..68532d9a04
--- /dev/null
+++ b/spec/ruby/library/set/include_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+require 'set'
+
+describe "Set#include?" do
+  it_behaves_like :set_include, :include?
+end
diff --git a/spec/ruby/library/set/initialize_clone_spec.rb b/spec/ruby/library/set/initialize_clone_spec.rb
new file mode 100644
index 0000000000..62985987fa
--- /dev/null
+++ b/spec/ruby/library/set/initialize_clone_spec.rb
@@ -0,0 +1,18 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#initialize_clone" do
+  ruby_version_is "3.0" do
+    # See https://bugs.ruby-lang.org/issues/14266
+    it "does not freeze the new Set when called from clone(freeze: false)" do
+      set1 = Set[1, 2]
+      set1.freeze
+      set2 = set1.clone(freeze: false)
+      set1.frozen?.should == true
+      set2.frozen?.should == false
+      set2.add 3
+      set1.should == Set[1, 2]
+      set2.should == Set[1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/initialize_spec.rb b/spec/ruby/library/set/initialize_spec.rb
new file mode 100644
index 0000000000..76ebc0a20a
--- /dev/null
+++ b/spec/ruby/library/set/initialize_spec.rb
@@ -0,0 +1,73 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#initialize" do
+  it "is private" do
+    Set.should have_private_instance_method(:initialize)
+  end
+
+  it "adds all elements of the passed Enumerable to self" do
+    s = Set.new([1, 2, 3])
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "uses #each_entry on the provided Enumerable" do
+    enumerable = MockObject.new('mock-enumerable')
+    enumerable.should_receive(:each_entry).and_yield(1).and_yield(2).and_yield(3)
+    s = Set.new(enumerable)
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "uses #each on the provided Enumerable if it does not respond to #each_entry" do
+    enumerable = MockObject.new('mock-enumerable')
+    enumerable.should_receive(:each).and_yield(1).and_yield(2).and_yield(3)
+    s = Set.new(enumerable)
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "raises if the provided Enumerable does not respond to #each_entry or #each" do
+    enumerable = MockObject.new('mock-enumerable')
+    -> { Set.new(enumerable) }.should raise_error(ArgumentError, "value must be enumerable")
+  end
+
+  it "should initialize with empty array and set" do
+    s = Set.new([])
+    s.size.should eql(0)
+
+    s = Set.new({})
+    s.size.should eql(0)
+  end
+
+  it "preprocesses all elements by a passed block before adding to self" do
+    s = Set.new([1, 2, 3]) { |x| x * x }
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(4)
+    s.should include(9)
+  end
+
+  it "should initialize with empty array and block" do
+    s = Set.new([]) { |x| x * x }
+    s.size.should eql(0)
+  end
+
+  it "should initialize with empty set and block" do
+    s = Set.new(Set.new) { |x| x * x }
+    s.size.should eql(0)
+  end
+
+  it "should initialize with just block" do
+    s = Set.new { |x| x * x }
+    s.size.should eql(0)
+    s.should eql(Set.new)
+  end
+end
diff --git a/spec/ruby/library/set/inspect_spec.rb b/spec/ruby/library/set/inspect_spec.rb
new file mode 100644
index 0000000000..4060c63b95
--- /dev/null
+++ b/spec/ruby/library/set/inspect_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/inspect'
+require 'set'
+
+describe "Set#inspect" do
+  it_behaves_like :set_inspect, :inspect
+end
diff --git a/spec/ruby/library/set/intersect_spec.rb b/spec/ruby/library/set/intersect_spec.rb
new file mode 100644
index 0000000000..e60f06db94
--- /dev/null
+++ b/spec/ruby/library/set/intersect_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#intersect?" do
+  it "returns true when two Sets have at least one element in common" do
+    Set[1, 2].intersect?(Set[2, 3]).should == true
+  end
+
+  it "returns false when two Sets have no element in common" do
+    Set[1, 2].intersect?(Set[3, 4]).should == false
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true when a Set has at least one element in common with a Set-like object" do
+      Set[1, 2].intersect?(SetSpecs::SetLike.new([2, 3])).should be_true
+    end
+
+    it "returns false when a Set has no element in common with a Set-like object" do
+      Set[1, 2].intersect?(SetSpecs::SetLike.new([3, 4])).should be_false
+    end
+  end
+end
diff --git a/spec/ruby/library/set/intersection_spec.rb b/spec/ruby/library/set/intersection_spec.rb
new file mode 100644
index 0000000000..792c2d8f07
--- /dev/null
+++ b/spec/ruby/library/set/intersection_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require_relative 'shared/intersection'
+require 'set'
+
+describe "Set#intersection" do
+  it_behaves_like :set_intersection, :intersection
+end
+
+describe "Set#&" do
+  it_behaves_like :set_intersection, :&
+end
diff --git a/spec/ruby/library/set/join_spec.rb b/spec/ruby/library/set/join_spec.rb
new file mode 100644
index 0000000000..7498a91d98
--- /dev/null
+++ b/spec/ruby/library/set/join_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../spec_helper'
+require 'set'
+
+ruby_version_is "3.0" do
+  describe "Set#join" do
+    it "returns an empty string if the Set is empty" do
+      Set[].join.should == ''
+    end
+
+    it "returns a new string formed by joining elements after conversion" do
+      set = Set[:a, :b, :c]
+      set.join.should == "abc"
+    end
+
+    it "does not separate elements when the passed separator is nil" do
+      set = Set[:a, :b, :c]
+      set.join(nil).should == "abc"
+    end
+
+    it "returns a string formed by concatenating each element separated by the separator" do
+      set = Set[:a, :b, :c]
+      set.join(' | ').should == "a | b | c"
+    end
+
+    it "calls #to_a to convert the Set in to an Array" do
+      set = Set[:a, :b, :c]
+      set.should_receive(:to_a).and_return([:a, :b, :c])
+      set.join.should == "abc"
+    end
+  end
+end
diff --git a/spec/ruby/library/set/keep_if_spec.rb b/spec/ruby/library/set/keep_if_spec.rb
new file mode 100644
index 0000000000..7edc80769f
--- /dev/null
+++ b/spec/ruby/library/set/keep_if_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#keep_if" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.keep_if { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "keeps every element from self for which the passed block returns true" do
+    @set.keep_if { |x| x.size != 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self" do
+    @set.keep_if {}.should equal(@set)
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.keep_if
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size != 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/library/set/length_spec.rb b/spec/ruby/library/set/length_spec.rb
new file mode 100644
index 0000000000..fef63d25a7
--- /dev/null
+++ b/spec/ruby/library/set/length_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/length'
+require 'set'
+
+describe "Set#length" do
+  it_behaves_like :set_length, :length
+end
diff --git a/spec/ruby/library/set/map_spec.rb b/spec/ruby/library/set/map_spec.rb
new file mode 100644
index 0000000000..e60e98b179
--- /dev/null
+++ b/spec/ruby/library/set/map_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/collect'
+
+describe "Set#map!" do
+  it_behaves_like :set_collect_bang, :map!
+end
diff --git a/spec/ruby/library/set/member_spec.rb b/spec/ruby/library/set/member_spec.rb
new file mode 100644
index 0000000000..5b56a38ab9
--- /dev/null
+++ b/spec/ruby/library/set/member_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+require 'set'
+
+describe "Set#member?" do
+  it_behaves_like :set_include, :member?
+end
diff --git a/spec/ruby/library/set/merge_spec.rb b/spec/ruby/library/set/merge_spec.rb
new file mode 100644
index 0000000000..a8e3ffc870
--- /dev/null
+++ b/spec/ruby/library/set/merge_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#merge" do
+  it "adds the elements of the passed Enumerable to self" do
+    Set[:a, :b].merge(Set[:b, :c, :d]).should == Set[:a, :b, :c, :d]
+    Set[1, 2].merge([3, 4]).should == Set[1, 2, 3, 4]
+  end
+
+  it "returns self" do
+    set = Set[1, 2]
+    set.merge([3, 4]).should equal(set)
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { Set[1, 2].merge(1) }.should raise_error(ArgumentError)
+    -> { Set[1, 2].merge(Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/minus_spec.rb b/spec/ruby/library/set/minus_spec.rb
new file mode 100644
index 0000000000..3fe0b6a2cc
--- /dev/null
+++ b/spec/ruby/library/set/minus_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require 'set'
+require_relative 'shared/difference'
+
+describe "Set#-" do
+  it_behaves_like :set_difference, :-
+end
diff --git a/spec/ruby/library/set/plus_spec.rb b/spec/ruby/library/set/plus_spec.rb
new file mode 100644
index 0000000000..3e70d3269d
--- /dev/null
+++ b/spec/ruby/library/set/plus_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/union'
+require 'set'
+
+describe "Set#+" do
+  it_behaves_like :set_union, :+
+end
diff --git a/spec/ruby/library/set/pretty_print_cycle_spec.rb b/spec/ruby/library/set/pretty_print_cycle_spec.rb
new file mode 100644
index 0000000000..4f440353e5
--- /dev/null
+++ b/spec/ruby/library/set/pretty_print_cycle_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#pretty_print_cycle" do
+  it "passes the 'pretty print' representation of a self-referencing Set to the pretty print writer" do
+    pp = mock("PrettyPrint")
+    pp.should_receive(:text).with("#<Set: {...}>")
+    Set[1, 2, 3].pretty_print_cycle(pp)
+  end
+end
diff --git a/spec/ruby/library/set/pretty_print_spec.rb b/spec/ruby/library/set/pretty_print_spec.rb
new file mode 100644
index 0000000000..ea9ead0df8
--- /dev/null
+++ b/spec/ruby/library/set/pretty_print_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require 'set'
+
+ruby_version_is ""..."3.1" do
+  describe "Set#pretty_print" do
+    it "passes the 'pretty print' representation of self to the pretty print writer" do
+      pp = mock("PrettyPrint")
+      set = Set[1, 2, 3]
+
+      pp.should_receive(:text).with("#<Set: {")
+      pp.should_receive(:text).with("}>")
+
+      pp.should_receive(:nest).with(1).and_yield
+      pp.should_receive(:seplist).with(set)
+
+      set.pretty_print(pp)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/proper_subset_spec.rb b/spec/ruby/library/set/proper_subset_spec.rb
new file mode 100644
index 0000000000..1f496a6199
--- /dev/null
+++ b/spec/ruby/library/set/proper_subset_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#proper_subset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that self is a proper subset of" do
+    Set[].proper_subset?(@set).should be_true
+    Set[].proper_subset?(Set[1, 2, 3]).should be_true
+    Set[].proper_subset?(Set["a", :b, ?c]).should be_true
+
+    Set[1, 2, 3].proper_subset?(@set).should be_true
+    Set[1, 3].proper_subset?(@set).should be_true
+    Set[1, 2].proper_subset?(@set).should be_true
+    Set[1].proper_subset?(@set).should be_true
+
+    Set[5].proper_subset?(@set).should be_false
+    Set[1, 5].proper_subset?(@set).should be_false
+    Set[nil].proper_subset?(@set).should be_false
+    Set["test"].proper_subset?(@set).should be_false
+
+    @set.proper_subset?(@set).should be_false
+    Set[].proper_subset?(Set[]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].proper_subset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true if passed a Set-like object that self is a proper subset of" do
+      Set[1, 2, 3].proper_subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/set/proper_superset_spec.rb b/spec/ruby/library/set/proper_superset_spec.rb
new file mode 100644
index 0000000000..a386c8c097
--- /dev/null
+++ b/spec/ruby/library/set/proper_superset_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#proper_superset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that self is a proper superset of" do
+    @set.proper_superset?(Set[]).should be_true
+    Set[1, 2, 3].proper_superset?(Set[]).should be_true
+    Set["a", :b, ?c].proper_superset?(Set[]).should be_true
+
+    @set.proper_superset?(Set[1, 2, 3]).should be_true
+    @set.proper_superset?(Set[1, 3]).should be_true
+    @set.proper_superset?(Set[1, 2]).should be_true
+    @set.proper_superset?(Set[1]).should be_true
+
+    @set.proper_superset?(Set[5]).should be_false
+    @set.proper_superset?(Set[1, 5]).should be_false
+    @set.proper_superset?(Set[nil]).should be_false
+    @set.proper_superset?(Set["test"]).should be_false
+
+    @set.proper_superset?(@set).should be_false
+    Set[].proper_superset?(Set[]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].proper_superset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true if passed a Set-like object that self is a proper superset of" do
+      Set[1, 2, 3, 4].proper_superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/set/reject_spec.rb b/spec/ruby/library/set/reject_spec.rb
new file mode 100644
index 0000000000..9131f960ad
--- /dev/null
+++ b/spec/ruby/library/set/reject_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#reject!" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.reject! { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "deletes every element from self for which the passed block returns true" do
+    @set.reject! { |x| x.size == 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self when self was modified" do
+    @set.reject! { |x| true }.should equal(@set)
+  end
+
+  it "returns nil when self was not modified" do
+    @set.reject! { |x| false }.should be_nil
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.reject!
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size == 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/library/set/replace_spec.rb b/spec/ruby/library/set/replace_spec.rb
new file mode 100644
index 0000000000..7511066c9c
--- /dev/null
+++ b/spec/ruby/library/set/replace_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#replace" do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "replaces the contents with other and returns self" do
+    @set.replace(Set[1, 2, 3]).should == @set
+    @set.should == Set[1, 2, 3]
+  end
+
+  it "accepts any enumerable as other" do
+    @set.replace([1, 2, 3]).should == Set[1, 2, 3]
+  end
+end
diff --git a/spec/ruby/library/set/select_spec.rb b/spec/ruby/library/set/select_spec.rb
new file mode 100644
index 0000000000..b458ffacaa
--- /dev/null
+++ b/spec/ruby/library/set/select_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/select'
+
+describe "Set#select!" do
+  it_behaves_like :set_select_bang, :select!
+end
diff --git a/spec/ruby/library/set/shared/add.rb b/spec/ruby/library/set/shared/add.rb
new file mode 100644
index 0000000000..9e797f5df9
--- /dev/null
+++ b/spec/ruby/library/set/shared/add.rb
@@ -0,0 +1,14 @@
+describe :set_add, shared: true do
+  before :each do
+    @set = Set.new
+  end
+
+  it "adds the passed Object to self" do
+    @set.send(@method, "dog")
+    @set.should include("dog")
+  end
+
+  it "returns self" do
+    @set.send(@method, "dog").should equal(@set)
+  end
+end
diff --git a/spec/ruby/library/set/shared/collect.rb b/spec/ruby/library/set/shared/collect.rb
new file mode 100644
index 0000000000..bc58c231be
--- /dev/null
+++ b/spec/ruby/library/set/shared/collect.rb
@@ -0,0 +1,20 @@
+describe :set_collect_bang, shared: true do
+  before :each do
+    @set = Set[1, 2, 3, 4, 5]
+  end
+
+  it "yields each Object in self" do
+    res = []
+    @set.send(@method) { |x| res << x }
+    res.sort.should == [1, 2, 3, 4, 5].sort
+  end
+
+  it "returns self" do
+    @set.send(@method) { |x| x }.should equal(@set)
+  end
+
+  it "replaces self with the return values of the block" do
+    @set.send(@method) { |x| x * 2 }
+    @set.should == Set[2, 4, 6, 8, 10]
+  end
+end
diff --git a/spec/ruby/library/set/shared/difference.rb b/spec/ruby/library/set/shared/difference.rb
new file mode 100644
index 0000000000..f88987ed2a
--- /dev/null
+++ b/spec/ruby/library/set/shared/difference.rb
@@ -0,0 +1,15 @@
+describe :set_difference, shared: true do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "returns a new Set containing self's elements excluding the elements in the passed Enumerable" do
+    @set.send(@method, Set[:a, :b]).should == Set[:c]
+    @set.send(@method, [:b, :c]).should == Set[:a]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/shared/include.rb b/spec/ruby/library/set/shared/include.rb
new file mode 100644
index 0000000000..b4d95cde24
--- /dev/null
+++ b/spec/ruby/library/set/shared/include.rb
@@ -0,0 +1,29 @@
+describe :set_include, shared: true do
+  it "returns true when self contains the passed Object" do
+    set = Set[:a, :b, :c]
+    set.send(@method, :a).should be_true
+    set.send(@method, :e).should be_false
+  end
+
+  describe "member equality" do
+    it "is checked using both #hash and #eql?" do
+      obj = Object.new
+      obj_another = Object.new
+
+      def obj.hash; 42 end
+      def obj_another.hash; 42 end
+      def obj_another.eql?(o) hash == o.hash end
+
+      set = Set["a", "b", "c", obj]
+      set.send(@method, obj_another).should == true
+    end
+
+    it "is not checked using #==" do
+      obj = Object.new
+      set = Set["a", "b", "c"]
+
+      obj.should_not_receive(:==)
+      set.send(@method, obj)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/shared/inspect.rb b/spec/ruby/library/set/shared/inspect.rb
new file mode 100644
index 0000000000..69fbdd12f6
--- /dev/null
+++ b/spec/ruby/library/set/shared/inspect.rb
@@ -0,0 +1,15 @@
+describe "set_inspect", shared: true do
+  it "returns a String representation of self" do
+    Set[].send(@method).should be_kind_of(String)
+    Set[nil, false, true].send(@method).should be_kind_of(String)
+    Set[1, 2, 3].send(@method).should be_kind_of(String)
+    Set["1", "2", "3"].send(@method).should be_kind_of(String)
+    Set[:a, "b", Set[?c]].send(@method).should be_kind_of(String)
+  end
+
+  it "correctly handles self-references" do
+    (set = Set[]) << set
+    set.send(@method).should be_kind_of(String)
+    set.send(@method).should include("#<Set: {...}>")
+  end
+end
diff --git a/spec/ruby/library/set/shared/intersection.rb b/spec/ruby/library/set/shared/intersection.rb
new file mode 100644
index 0000000000..5ae4199c94
--- /dev/null
+++ b/spec/ruby/library/set/shared/intersection.rb
@@ -0,0 +1,15 @@
+describe :set_intersection, shared: true do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "returns a new Set containing only elements shared by self and the passed Enumerable" do
+    @set.send(@method, Set[:b, :c, :d, :e]).should == Set[:b, :c]
+    @set.send(@method, [:b, :c, :d]).should == Set[:b, :c]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/shared/length.rb b/spec/ruby/library/set/shared/length.rb
new file mode 100644
index 0000000000..a8fcee9f39
--- /dev/null
+++ b/spec/ruby/library/set/shared/length.rb
@@ -0,0 +1,6 @@
+describe :set_length, shared: true do
+  it "returns the number of elements in the set" do
+    set = Set[:a, :b, :c]
+    set.send(@method).should == 3
+  end
+end
diff --git a/spec/ruby/library/set/shared/select.rb b/spec/ruby/library/set/shared/select.rb
new file mode 100644
index 0000000000..2108d398b4
--- /dev/null
+++ b/spec/ruby/library/set/shared/select.rb
@@ -0,0 +1,42 @@
+require_relative '../../../spec_helper'
+require 'set'
+
+describe :set_select_bang, shared: true do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.send(@method) { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "keeps every element from self for which the passed block returns true" do
+    @set.send(@method) { |x| x.size != 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self when self was modified" do
+    @set.send(@method) { false }.should equal(@set)
+  end
+
+  it "returns nil when self was not modified" do
+    @set.send(@method) { true }.should be_nil
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.send(@method)
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size != 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/library/set/shared/union.rb b/spec/ruby/library/set/shared/union.rb
new file mode 100644
index 0000000000..314f0e852d
--- /dev/null
+++ b/spec/ruby/library/set/shared/union.rb
@@ -0,0 +1,15 @@
+describe :set_union, shared: true do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "returns a new Set containing all elements of self and the passed Enumerable" do
+    @set.send(@method, Set[:b, :d, :e]).should == Set[:a, :b, :c, :d, :e]
+    @set.send(@method, [:b, :e]).should == Set[:a, :b, :c, :e]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/size_spec.rb b/spec/ruby/library/set/size_spec.rb
new file mode 100644
index 0000000000..3c8cb38517
--- /dev/null
+++ b/spec/ruby/library/set/size_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'shared/length'
+require 'set'
+
+describe "Set#size" do
+  it_behaves_like :set_length, :size
+end
diff --git a/spec/ruby/library/set/sortedset/add_spec.rb b/spec/ruby/library/set/sortedset/add_spec.rb
new file mode 100644
index 0000000000..4f3bb252e1
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/add_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/add'
+
+  describe "SortedSet#add" do
+    it_behaves_like :sorted_set_add, :add
+
+    it "takes only values which responds <=>" do
+      obj = mock('no_comparison_operator')
+      obj.stub!(:respond_to?).with(:<=>).and_return(false)
+      -> { SortedSet["hello"].add(obj) }.should raise_error(ArgumentError)
+    end
+
+    it "raises on incompatible <=> comparison" do
+      # Use #to_a here as elements are sorted only when needed.
+      # Therefore the <=> incompatibility is only noticed on sorting.
+      -> { SortedSet['1', '2'].add(3).to_a }.should raise_error(ArgumentError)
+    end
+  end
+
+  describe "SortedSet#add?" do
+    before :each do
+      @set = SortedSet.new
+    end
+
+    it "adds the passed Object to self" do
+      @set.add?("cat")
+      @set.should include("cat")
+    end
+
+    it "returns self when the Object has not yet been added to self" do
+      @set.add?("cat").should equal(@set)
+    end
+
+    it "returns nil when the Object has already been added to self" do
+      @set.add?("cat")
+      @set.add?("cat").should be_nil
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/append_spec.rb b/spec/ruby/library/set/sortedset/append_spec.rb
new file mode 100644
index 0000000000..d72d70b21f
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/append_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/add'
+
+  describe "SortedSet#<<" do
+    it_behaves_like :sorted_set_add, :<<
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/case_equality_spec.rb b/spec/ruby/library/set/sortedset/case_equality_spec.rb
new file mode 100644
index 0000000000..d7c296b626
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/case_equality_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/include'
+  require 'set'
+
+  describe "SortedSet#===" do
+    it_behaves_like :sorted_set_include, :===
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/classify_spec.rb b/spec/ruby/library/set/sortedset/classify_spec.rb
new file mode 100644
index 0000000000..4011e58b82
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/classify_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#classify" do
+    before :each do
+      @set = SortedSet["one", "two", "three", "four"]
+    end
+
+    it "yields each Object in self in sorted order" do
+      res = []
+      @set.classify { |x| res << x }
+      res.should == ["one", "two", "three", "four"].sort
+    end
+
+    it "returns an Enumerator when passed no block" do
+      enum = @set.classify
+      enum.should be_an_instance_of(Enumerator)
+
+      classified = enum.each { |x| x.length }
+      classified.should == { 3 => SortedSet["one", "two"], 4 => SortedSet["four"], 5 => SortedSet["three"] }
+    end
+
+    it "classifies the Objects in self based on the block's return value" do
+      classified = @set.classify { |x| x.length }
+      classified.should == { 3 => SortedSet["one", "two"], 4 => SortedSet["four"], 5 => SortedSet["three"] }
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/clear_spec.rb b/spec/ruby/library/set/sortedset/clear_spec.rb
new file mode 100644
index 0000000000..879aa824d8
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/clear_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#clear" do
+    before :each do
+      @set = SortedSet["one", "two", "three", "four"]
+    end
+
+    it "removes all elements from self" do
+      @set.clear
+      @set.should be_empty
+    end
+
+    it "returns self" do
+      @set.clear.should equal(@set)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/collect_spec.rb b/spec/ruby/library/set/sortedset/collect_spec.rb
new file mode 100644
index 0000000000..0674f0d130
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/collect_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/collect'
+
+  describe "SortedSet#collect!" do
+    it_behaves_like :sorted_set_collect_bang, :collect!
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/constructor_spec.rb b/spec/ruby/library/set/sortedset/constructor_spec.rb
new file mode 100644
index 0000000000..31f30fd892
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/constructor_spec.rb
@@ -0,0 +1,18 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet[]" do
+    it "returns a new SortedSet populated with the passed Objects" do
+      set = SortedSet[1, 2, 3]
+
+      set.instance_of?(SortedSet).should be_true
+      set.size.should eql(3)
+
+      set.should include(1)
+      set.should include(2)
+      set.should include(3)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/delete_if_spec.rb b/spec/ruby/library/set/sortedset/delete_if_spec.rb
new file mode 100644
index 0000000000..787639ae12
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/delete_if_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#delete_if" do
+    before :each do
+      @set = SortedSet["one", "two", "three"]
+    end
+
+    it "yields each Object in self in sorted order" do
+      ret = []
+      @set.delete_if { |x| ret << x }
+      ret.should == ["one", "two", "three"].sort
+    end
+
+    it "deletes every element from self for which the passed block returns true" do
+      @set.delete_if { |x| x.size == 3 }
+      @set.size.should eql(1)
+
+      @set.should_not include("one")
+      @set.should_not include("two")
+      @set.should include("three")
+    end
+
+    it "returns self" do
+      @set.delete_if { |x| x }.should equal(@set)
+    end
+
+    it "returns an Enumerator when passed no block" do
+      enum = @set.delete_if
+      enum.should be_an_instance_of(Enumerator)
+
+      enum.each { |x| x.size == 3 }
+
+      @set.should_not include("one")
+      @set.should_not include("two")
+      @set.should include("three")
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/delete_spec.rb b/spec/ruby/library/set/sortedset/delete_spec.rb
new file mode 100644
index 0000000000..0e2a6accf3
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/delete_spec.rb
@@ -0,0 +1,40 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#delete" do
+    before :each do
+      @set = SortedSet["a", "b", "c"]
+    end
+
+    it "deletes the passed Object from self" do
+      @set.delete("a")
+      @set.should_not include("a")
+    end
+
+    it "returns self" do
+      @set.delete("a").should equal(@set)
+      @set.delete("x").should equal(@set)
+    end
+  end
+
+  describe "SortedSet#delete?" do
+    before :each do
+      @set = SortedSet["a", "b", "c"]
+    end
+
+    it "deletes the passed Object from self" do
+      @set.delete?("a")
+      @set.should_not include("a")
+    end
+
+    it "returns self when the passed Object is in self" do
+      @set.delete?("a").should equal(@set)
+    end
+
+    it "returns nil when the passed Object is not in self" do
+      @set.delete?("x").should be_nil
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/difference_spec.rb b/spec/ruby/library/set/sortedset/difference_spec.rb
new file mode 100644
index 0000000000..fb064bdff9
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/difference_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/difference'
+
+  describe "SortedSet#difference" do
+    it_behaves_like :sorted_set_difference, :difference
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/divide_spec.rb b/spec/ruby/library/set/sortedset/divide_spec.rb
new file mode 100644
index 0000000000..31ab6037e4
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/divide_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#divide" do
+    it "divides self into a set of subsets based on the blocks return values" do
+      set = SortedSet["one", "two", "three", "four", "five"].divide { |x| x.length }
+      set.map { |x| x.to_a }.to_a.sort.should == [["five", "four"], ["one", "two"], ["three"]]
+    end
+
+    it "yields each Object in self in sorted order" do
+      ret = []
+      SortedSet["one", "two", "three", "four", "five"].divide { |x| ret << x }
+      ret.should == ["one", "two", "three", "four", "five"].sort
+    end
+
+    # BUG: Does not raise a LocalJumpError, but a NoMethodError
+    #
+    # it "raises a LocalJumpError when not passed a block" do
+    #   lambda { SortedSet[1].divide }.should raise_error(LocalJumpError)
+    # end
+  end
+
+  describe "SortedSet#divide when passed a block with an arity of 2" do
+    it "divides self into a set of subsets based on the blocks return values" do
+      set = SortedSet[1, 3, 4, 6, 9, 10, 11].divide { |x, y| (x - y).abs == 1 }
+      set.map { |x| x.to_a }.to_a.sort.should == [[1], [3, 4], [6], [9, 10, 11]]
+    end
+
+    it "yields each two Objects to the block" do
+      ret = []
+      SortedSet[1, 2].divide { |x, y| ret << [x, y] }
+      ret.should == [[1, 1], [1, 2], [2, 1], [2, 2]]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/each_spec.rb b/spec/ruby/library/set/sortedset/each_spec.rb
new file mode 100644
index 0000000000..79d8aee223
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/each_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#each" do
+    before :each do
+      @set = SortedSet[1, 2, 3]
+    end
+
+    it "yields each Object in self in sorted order" do
+      ret = []
+      SortedSet["one", "two", "three"].each { |x| ret << x }
+      ret.should == ["one", "two", "three"].sort
+    end
+
+    it "returns self" do
+      @set.each { |x| x }.should equal(@set)
+    end
+
+    it "returns an Enumerator when not passed a block" do
+      enum = @set.each
+
+      ret = []
+      enum.each { |x| ret << x }
+      ret.sort.should == [1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/empty_spec.rb b/spec/ruby/library/set/sortedset/empty_spec.rb
new file mode 100644
index 0000000000..2e52c3e81a
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/empty_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#empty?" do
+    it "returns true if self is empty" do
+      SortedSet[].empty?.should be_true
+      SortedSet[1].empty?.should be_false
+      SortedSet[1,2,3].empty?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/eql_spec.rb b/spec/ruby/library/set/sortedset/eql_spec.rb
new file mode 100644
index 0000000000..050464994b
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/eql_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#eql?" do
+    it "returns true when the passed argument is a SortedSet and contains the same elements" do
+      SortedSet[].should eql(SortedSet[])
+      SortedSet[1, 2, 3].should eql(SortedSet[1, 2, 3])
+      SortedSet[1, 2, 3].should eql(SortedSet[3, 2, 1])
+
+  #    SortedSet["a", :b, ?c].should eql(SortedSet[?c, :b, "a"])
+
+      SortedSet[1, 2, 3].should_not eql(SortedSet[1.0, 2, 3])
+      SortedSet[1, 2, 3].should_not eql(SortedSet[2, 3])
+      SortedSet[1, 2, 3].should_not eql(SortedSet[])
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/equal_value_spec.rb b/spec/ruby/library/set/sortedset/equal_value_spec.rb
new file mode 100644
index 0000000000..30422f5b95
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/equal_value_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#==" do
+    it "returns true when the passed Object is a SortedSet and self and the Object contain the same elements" do
+      SortedSet[].should == SortedSet[]
+      SortedSet[1, 2, 3].should == SortedSet[1, 2, 3]
+      SortedSet["1", "2", "3"].should == SortedSet["1", "2", "3"]
+
+      SortedSet[1, 2, 3].should_not == SortedSet[1.0, 2, 3]
+      SortedSet[1, 2, 3].should_not == [1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/exclusion_spec.rb b/spec/ruby/library/set/sortedset/exclusion_spec.rb
new file mode 100644
index 0000000000..1967dfbfa6
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/exclusion_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#^" do
+    before :each do
+      @set = SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns a new SortedSet containing elements that are not in both self and the passed Enumerable" do
+      (@set ^ SortedSet[3, 4, 5]).should == SortedSet[1, 2, 5]
+      (@set ^ [3, 4, 5]).should == SortedSet[1, 2, 5]
+    end
+
+    it "raises an ArgumentError when passed a non-Enumerable" do
+      -> { @set ^ 3 }.should raise_error(ArgumentError)
+      -> { @set ^ Object.new }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/filter_spec.rb b/spec/ruby/library/set/sortedset/filter_spec.rb
new file mode 100644
index 0000000000..3b9dcb63c9
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/filter_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/select'
+  require 'set'
+
+  describe "SortedSet#filter!" do
+    it_behaves_like :sorted_set_select_bang, :filter!
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/flatten_merge_spec.rb b/spec/ruby/library/set/sortedset/flatten_merge_spec.rb
new file mode 100644
index 0000000000..0d67cb331e
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/flatten_merge_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#flatten_merge" do
+    it "is protected" do
+      SortedSet.should have_protected_instance_method("flatten_merge")
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/flatten_spec.rb b/spec/ruby/library/set/sortedset/flatten_spec.rb
new file mode 100644
index 0000000000..e83ad1044a
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/flatten_spec.rb
@@ -0,0 +1,47 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  # Note: Flatten make little sens on sorted sets, because SortedSets are not (by default)
+  # comparable. For a SortedSet to be both valid and nested, we need to define a comparison operator:
+  module SortedSet_FlattenSpecs
+    class ComparableSortedSet < SortedSet
+      def <=>(other)
+        return puts "#{other} vs #{self}" unless other.is_a?(ComparableSortedSet)
+        to_a <=> other.to_a
+      end
+    end
+  end
+
+  describe "SortedSet#flatten" do
+    it "returns a copy of self with each included SortedSet flattened" do
+      klass = SortedSet_FlattenSpecs::ComparableSortedSet
+      set = klass[klass[1,2], klass[3,4], klass[5,6,7], klass[8]]
+      flattened_set = set.flatten
+
+      flattened_set.should_not equal(set)
+      flattened_set.should == klass[1, 2, 3, 4, 5, 6, 7, 8]
+    end
+  end
+
+  describe "SortedSet#flatten!" do
+    it "flattens self" do
+      klass = SortedSet_FlattenSpecs::ComparableSortedSet
+      set = klass[klass[1,2], klass[3,4], klass[5,6,7], klass[8]]
+      set.flatten!
+      set.should == klass[1, 2, 3, 4, 5, 6, 7, 8]
+    end
+
+    it "returns self when self was modified" do
+      klass = SortedSet_FlattenSpecs::ComparableSortedSet
+      set = klass[klass[1,2], klass[3,4]]
+      set.flatten!.should equal(set)
+    end
+
+    it "returns nil when self was not modified" do
+      set = SortedSet[1, 2, 3, 4]
+      set.flatten!.should be_nil
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/hash_spec.rb b/spec/ruby/library/set/sortedset/hash_spec.rb
new file mode 100644
index 0000000000..40676de7fc
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/hash_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#hash" do
+    it "is static" do
+      SortedSet[].hash.should == SortedSet[].hash
+      SortedSet[1, 2, 3].hash.should == SortedSet[1, 2, 3].hash
+      SortedSet["a", "b", "c"].hash.should == SortedSet["c", "b", "a"].hash
+
+      SortedSet[].hash.should_not == SortedSet[1, 2, 3].hash
+      SortedSet[1, 2, 3].hash.should_not == SortedSet["a", "b", "c"].hash
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/include_spec.rb b/spec/ruby/library/set/sortedset/include_spec.rb
new file mode 100644
index 0000000000..ec2ad987d5
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/include_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/include'
+  require 'set'
+
+  describe "SortedSet#include?" do
+    it_behaves_like :sorted_set_include, :include?
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/initialize_spec.rb b/spec/ruby/library/set/sortedset/initialize_spec.rb
new file mode 100644
index 0000000000..4d1707b72a
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/initialize_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#initialize" do
+    it "is private" do
+      SortedSet.should have_private_instance_method("initialize")
+    end
+
+    it "adds all elements of the passed Enumerable to self" do
+      s = SortedSet.new([1, 2, 3])
+      s.size.should eql(3)
+      s.should include(1)
+      s.should include(2)
+      s.should include(3)
+    end
+
+    it "preprocesses all elements by a passed block before adding to self" do
+      s = SortedSet.new([1, 2, 3]) { |x| x * x }
+      s.size.should eql(3)
+      s.should include(1)
+      s.should include(4)
+      s.should include(9)
+    end
+
+    it "raises on incompatible <=> comparison" do
+      # Use #to_a here as elements are sorted only when needed.
+      # Therefore the <=> incompatibility is only noticed on sorting.
+      -> { SortedSet.new(['00', nil]).to_a }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/inspect_spec.rb b/spec/ruby/library/set/sortedset/inspect_spec.rb
new file mode 100644
index 0000000000..1c4dd9e6e2
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/inspect_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#inspect" do
+    it "returns a String representation of self" do
+      SortedSet[].inspect.should be_kind_of(String)
+      SortedSet[1, 2, 3].inspect.should be_kind_of(String)
+      SortedSet["1", "2", "3"].inspect.should be_kind_of(String)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/intersection_spec.rb b/spec/ruby/library/set/sortedset/intersection_spec.rb
new file mode 100644
index 0000000000..6daa271b73
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/intersection_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/intersection'
+  require 'set'
+
+  describe "SortedSet#intersection" do
+    it_behaves_like :sorted_set_intersection, :intersection
+  end
+
+  describe "SortedSet#&" do
+    it_behaves_like :sorted_set_intersection, :&
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/keep_if_spec.rb b/spec/ruby/library/set/sortedset/keep_if_spec.rb
new file mode 100644
index 0000000000..3e5f3bbc47
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/keep_if_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#keep_if" do
+    before :each do
+      @set = SortedSet["one", "two", "three"]
+    end
+
+    it "yields each Object in self in sorted order" do
+      ret = []
+      @set.keep_if { |x| ret << x }
+      ret.should == ["one", "two", "three"].sort
+    end
+
+    it "keeps every element from self for which the passed block returns true" do
+      @set.keep_if { |x| x.size != 3 }
+      @set.to_a.should == ["three"]
+    end
+
+    it "returns self" do
+      @set.keep_if {}.should equal(@set)
+    end
+
+    it "returns an Enumerator when passed no block" do
+      enum = @set.keep_if
+      enum.should be_an_instance_of(Enumerator)
+
+      enum.each { |x| x.size != 3 }
+      @set.to_a.should == ["three"]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/length_spec.rb b/spec/ruby/library/set/sortedset/length_spec.rb
new file mode 100644
index 0000000000..de6791f6bb
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/length_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/length'
+  require 'set'
+
+  describe "SortedSet#length" do
+    it_behaves_like :sorted_set_length, :length
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/map_spec.rb b/spec/ruby/library/set/sortedset/map_spec.rb
new file mode 100644
index 0000000000..4971b9529b
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/map_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/collect'
+
+  describe "SortedSet#map!" do
+    it_behaves_like :sorted_set_collect_bang, :map!
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/member_spec.rb b/spec/ruby/library/set/sortedset/member_spec.rb
new file mode 100644
index 0000000000..142b09b651
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/member_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/include'
+  require 'set'
+
+  describe "SortedSet#member?" do
+    it_behaves_like :sorted_set_include, :member?
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/merge_spec.rb b/spec/ruby/library/set/sortedset/merge_spec.rb
new file mode 100644
index 0000000000..c4cbc6d2b4
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/merge_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#merge" do
+    it "adds the elements of the passed Enumerable to self" do
+      SortedSet["a", "b"].merge(SortedSet["b", "c", "d"]).should == SortedSet["a", "b", "c", "d"]
+      SortedSet[1, 2].merge([3, 4]).should == SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns self" do
+      set = SortedSet[1, 2]
+      set.merge([3, 4]).should equal(set)
+    end
+
+    it "raises an ArgumentError when passed a non-Enumerable" do
+      -> { SortedSet[1, 2].merge(1) }.should raise_error(ArgumentError)
+      -> { SortedSet[1, 2].merge(Object.new) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/minus_spec.rb b/spec/ruby/library/set/sortedset/minus_spec.rb
new file mode 100644
index 0000000000..d6abc5e204
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/minus_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+  require_relative 'shared/difference'
+
+  describe "SortedSet#-" do
+    it_behaves_like :sorted_set_difference, :-
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/plus_spec.rb b/spec/ruby/library/set/sortedset/plus_spec.rb
new file mode 100644
index 0000000000..13fc873ad1
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/plus_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/union'
+  require 'set'
+
+  describe "SortedSet#+" do
+    it_behaves_like :sorted_set_union, :+
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb b/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb
new file mode 100644
index 0000000000..e97f509406
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#pretty_print_cycle" do
+    it "passes the 'pretty print' representation of a self-referencing SortedSet to the pretty print writer" do
+      pp = mock("PrettyPrint")
+      pp.should_receive(:text).with("#<SortedSet: {...}>")
+      SortedSet[1, 2, 3].pretty_print_cycle(pp)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/pretty_print_spec.rb b/spec/ruby/library/set/sortedset/pretty_print_spec.rb
new file mode 100644
index 0000000000..a8088bf797
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/pretty_print_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#pretty_print" do
+    it "passes the 'pretty print' representation of self to the pretty print writer" do
+      pp = mock("PrettyPrint")
+      set = SortedSet[1, 2, 3]
+
+      pp.should_receive(:text).with("#<SortedSet: {")
+      pp.should_receive(:text).with("}>")
+
+      pp.should_receive(:nest).with(1).and_yield
+      pp.should_receive(:seplist).with(set)
+
+      set.pretty_print(pp)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/proper_subset_spec.rb b/spec/ruby/library/set/sortedset/proper_subset_spec.rb
new file mode 100644
index 0000000000..34fb89d13d
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/proper_subset_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#proper_subset?" do
+    before :each do
+      @set = SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns true if passed a SortedSet that self is a proper subset of" do
+      SortedSet[].proper_subset?(@set).should be_true
+      SortedSet[].proper_subset?(SortedSet[1, 2, 3]).should be_true
+      SortedSet[].proper_subset?(SortedSet["a", "b", "c"]).should be_true
+
+      SortedSet[1, 2, 3].proper_subset?(@set).should be_true
+      SortedSet[1, 3].proper_subset?(@set).should be_true
+      SortedSet[1, 2].proper_subset?(@set).should be_true
+      SortedSet[1].proper_subset?(@set).should be_true
+
+      SortedSet[5].proper_subset?(@set).should be_false
+      SortedSet[1, 5].proper_subset?(@set).should be_false
+      SortedSet["test"].proper_subset?(@set).should be_false
+
+      @set.proper_subset?(@set).should be_false
+      SortedSet[].proper_subset?(SortedSet[]).should be_false
+    end
+
+    it "raises an ArgumentError when passed a non-SortedSet" do
+      -> { SortedSet[].proper_subset?([]) }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_subset?(1) }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_subset?("test") }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_subset?(Object.new) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/proper_superset_spec.rb b/spec/ruby/library/set/sortedset/proper_superset_spec.rb
new file mode 100644
index 0000000000..8b92444f72
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/proper_superset_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#proper_superset?" do
+    before :each do
+      @set = SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns true if passed a SortedSet that self is a proper superset of" do
+      @set.proper_superset?(SortedSet[]).should be_true
+      SortedSet[1, 2, 3].proper_superset?(SortedSet[]).should be_true
+      SortedSet["a", "b", "c"].proper_superset?(SortedSet[]).should be_true
+
+      @set.proper_superset?(SortedSet[1, 2, 3]).should be_true
+      @set.proper_superset?(SortedSet[1, 3]).should be_true
+      @set.proper_superset?(SortedSet[1, 2]).should be_true
+      @set.proper_superset?(SortedSet[1]).should be_true
+
+      @set.proper_superset?(SortedSet[5]).should be_false
+      @set.proper_superset?(SortedSet[1, 5]).should be_false
+      @set.proper_superset?(SortedSet["test"]).should be_false
+
+      @set.proper_superset?(@set).should be_false
+      SortedSet[].proper_superset?(SortedSet[]).should be_false
+    end
+
+    it "raises an ArgumentError when passed a non-SortedSet" do
+      -> { SortedSet[].proper_superset?([]) }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_superset?(1) }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_superset?("test") }.should raise_error(ArgumentError)
+      -> { SortedSet[].proper_superset?(Object.new) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/reject_spec.rb b/spec/ruby/library/set/sortedset/reject_spec.rb
new file mode 100644
index 0000000000..396b864cc5
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/reject_spec.rb
@@ -0,0 +1,45 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#reject!" do
+    before :each do
+      @set = SortedSet["one", "two", "three"]
+    end
+
+    it "yields each Object in self in sorted order" do
+      res = []
+      @set.reject! { |x| res << x }
+      res.should == ["one", "two", "three"].sort
+    end
+
+    it "deletes every element from self for which the passed block returns true" do
+      @set.reject! { |x| x.size == 3 }
+      @set.size.should eql(1)
+
+      @set.should_not include("one")
+      @set.should_not include("two")
+      @set.should include("three")
+    end
+
+    it "returns self when self was modified" do
+      @set.reject! { |x| true }.should equal(@set)
+    end
+
+    it "returns nil when self was not modified" do
+      @set.reject! { |x| false }.should be_nil
+    end
+
+    it "returns an Enumerator when passed no block" do
+      enum = @set.reject!
+      enum.should be_an_instance_of(Enumerator)
+
+      enum.each { |x| x.size == 3 }
+
+      @set.should_not include("one")
+      @set.should_not include("two")
+      @set.should include("three")
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/replace_spec.rb b/spec/ruby/library/set/sortedset/replace_spec.rb
new file mode 100644
index 0000000000..2900221c01
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/replace_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#replace" do
+    before :each do
+      @set = SortedSet["a", "b", "c"]
+    end
+
+    it "replaces the contents with other and returns self" do
+      @set.replace(SortedSet[1, 2, 3]).should == @set
+      @set.should == SortedSet[1, 2, 3]
+    end
+
+    it "accepts any enumerable as other" do
+      @set.replace([1, 2, 3]).should == SortedSet[1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/select_spec.rb b/spec/ruby/library/set/sortedset/select_spec.rb
new file mode 100644
index 0000000000..fc4c15ee4d
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/select_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/select'
+  require 'set'
+
+  describe "SortedSet#select!" do
+    it_behaves_like :sorted_set_select_bang, :select!
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/add.rb b/spec/ruby/library/set/sortedset/shared/add.rb
new file mode 100644
index 0000000000..95ef1b090e
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/add.rb
@@ -0,0 +1,14 @@
+describe :sorted_set_add, shared: true do
+  before :each do
+    @set = SortedSet.new
+  end
+
+  it "adds the passed Object to self" do
+    @set.send(@method, "dog")
+    @set.should include("dog")
+  end
+
+  it "returns self" do
+    @set.send(@method, "dog").should equal(@set)
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/collect.rb b/spec/ruby/library/set/sortedset/shared/collect.rb
new file mode 100644
index 0000000000..e53304d427
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/collect.rb
@@ -0,0 +1,20 @@
+describe :sorted_set_collect_bang, shared: true do
+  before :each do
+    @set = SortedSet[1, 2, 3, 4, 5]
+  end
+
+  it "yields each Object in self in sorted order" do
+    res = []
+    SortedSet["one", "two", "three"].send(@method) { |x| res << x; x }
+    res.should == ["one", "two", "three"].sort
+  end
+
+  it "returns self" do
+    @set.send(@method) { |x| x }.should equal(@set)
+  end
+
+  it "replaces self with the return values of the block" do
+    @set.send(@method) { |x| x * 2 }
+    @set.should == SortedSet[2, 4, 6, 8, 10]
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/difference.rb b/spec/ruby/library/set/sortedset/shared/difference.rb
new file mode 100644
index 0000000000..688e23a7a7
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/difference.rb
@@ -0,0 +1,15 @@
+describe :sorted_set_difference, shared: true do
+  before :each do
+    @set = SortedSet["a", "b", "c"]
+  end
+
+  it "returns a new SortedSet containing self's elements excluding the elements in the passed Enumerable" do
+    @set.send(@method, SortedSet["a", "b"]).should == SortedSet["c"]
+    @set.send(@method, ["b", "c"]).should == SortedSet["a"]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/include.rb b/spec/ruby/library/set/sortedset/shared/include.rb
new file mode 100644
index 0000000000..cd1758819d
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/include.rb
@@ -0,0 +1,7 @@
+describe :sorted_set_include, shared: true do
+  it "returns true when self contains the passed Object" do
+    set = SortedSet["a", "b", "c"]
+    set.send(@method, "a").should be_true
+    set.send(@method, "e").should be_false
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/intersection.rb b/spec/ruby/library/set/sortedset/shared/intersection.rb
new file mode 100644
index 0000000000..045716ad05
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/intersection.rb
@@ -0,0 +1,15 @@
+describe :sorted_set_intersection, shared: true do
+  before :each do
+    @set = SortedSet["a", "b", "c"]
+  end
+
+  it "returns a new SortedSet containing only elements shared by self and the passed Enumerable" do
+    @set.send(@method, SortedSet["b", "c", "d", "e"]).should == SortedSet["b", "c"]
+    @set.send(@method, ["b", "c", "d"]).should == SortedSet["b", "c"]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/length.rb b/spec/ruby/library/set/sortedset/shared/length.rb
new file mode 100644
index 0000000000..d1dfee1cff
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/length.rb
@@ -0,0 +1,6 @@
+describe :sorted_set_length, shared: true do
+  it "returns the number of elements in the set" do
+    set = SortedSet["a", "b", "c"]
+    set.send(@method).should == 3
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/select.rb b/spec/ruby/library/set/sortedset/shared/select.rb
new file mode 100644
index 0000000000..e13311eda5
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/select.rb
@@ -0,0 +1,35 @@
+require_relative '../../../../spec_helper'
+require 'set'
+
+describe :sorted_set_select_bang, shared: true do
+  before :each do
+    @set = SortedSet["one", "two", "three"]
+  end
+
+  it "yields each Object in self in sorted order" do
+    res = []
+    @set.send(@method) { |x| res << x }
+    res.should == ["one", "two", "three"].sort
+  end
+
+  it "keeps every element from self for which the passed block returns true" do
+    @set.send(@method) { |x| x.size != 3 }
+    @set.to_a.should == ["three"]
+  end
+
+  it "returns self when self was modified" do
+    @set.send(@method) { false }.should equal(@set)
+  end
+
+  it "returns nil when self was not modified" do
+    @set.send(@method) { true }.should be_nil
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.send(@method)
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size != 3 }
+    @set.to_a.should == ["three"]
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/shared/union.rb b/spec/ruby/library/set/sortedset/shared/union.rb
new file mode 100644
index 0000000000..9015bdc8e3
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/shared/union.rb
@@ -0,0 +1,15 @@
+describe :sorted_set_union, shared: true do
+  before :each do
+    @set = SortedSet["a", "b", "c"]
+  end
+
+  it "returns a new SortedSet containing all elements of self and the passed Enumerable" do
+    @set.send(@method, SortedSet["b", "d", "e"]).should == SortedSet["a", "b", "c", "d", "e"]
+    @set.send(@method, ["b", "e"]).should == SortedSet["a", "b", "c", "e"]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/size_spec.rb b/spec/ruby/library/set/sortedset/size_spec.rb
new file mode 100644
index 0000000000..d908b33b53
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/size_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/length'
+  require 'set'
+
+  describe "SortedSet#size" do
+    it_behaves_like :sorted_set_length, :size
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/sortedset_spec.rb b/spec/ruby/library/set/sortedset/sortedset_spec.rb
new file mode 100644
index 0000000000..3ead5495fc
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/sortedset_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../../spec_helper'
+require 'set'
+
+ruby_version_is "3.0" do
+  describe "SortedSet" do
+    it "raises error including message that it has been extracted from the set stdlib" do
+      -> {
+        SortedSet
+      }.should raise_error(RuntimeError) { |e|
+        e.message.should.include?("The `SortedSet` class has been extracted from the `set` library")
+      }
+    end
+  end
+end
+
+ruby_version_is ""..."3.0" do
+  describe "SortedSet" do
+    it "is part of the set stdlib" do
+      SortedSet.superclass.should == Set
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/subset_spec.rb b/spec/ruby/library/set/sortedset/subset_spec.rb
new file mode 100644
index 0000000000..272e3f985e
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/subset_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#subset?" do
+    before :each do
+      @set = SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns true if passed a SortedSet that is equal to self or self is a subset of" do
+      @set.subset?(@set).should be_true
+      SortedSet[].subset?(SortedSet[]).should be_true
+
+      SortedSet[].subset?(@set).should be_true
+      SortedSet[].subset?(SortedSet[1, 2, 3]).should be_true
+      SortedSet[].subset?(SortedSet["a", "b", "c"]).should be_true
+
+      SortedSet[1, 2, 3].subset?(@set).should be_true
+      SortedSet[1, 3].subset?(@set).should be_true
+      SortedSet[1, 2].subset?(@set).should be_true
+      SortedSet[1].subset?(@set).should be_true
+
+      SortedSet[5].subset?(@set).should be_false
+      SortedSet[1, 5].subset?(@set).should be_false
+      SortedSet["test"].subset?(@set).should be_false
+    end
+
+    it "raises an ArgumentError when passed a non-SortedSet" do
+      -> { SortedSet[].subset?([]) }.should raise_error(ArgumentError)
+      -> { SortedSet[].subset?(1) }.should raise_error(ArgumentError)
+      -> { SortedSet[].subset?("test") }.should raise_error(ArgumentError)
+      -> { SortedSet[].subset?(Object.new) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/subtract_spec.rb b/spec/ruby/library/set/sortedset/subtract_spec.rb
new file mode 100644
index 0000000000..b2af127f89
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/subtract_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#subtract" do
+    before :each do
+      @set = SortedSet["a", "b", "c"]
+    end
+
+    it "deletes any elements contained in other and returns self" do
+      @set.subtract(SortedSet["b", "c"]).should == @set
+      @set.should == SortedSet["a"]
+    end
+
+    it "accepts any enumerable as other" do
+      @set.subtract(["c"]).should == SortedSet["a", "b"]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/superset_spec.rb b/spec/ruby/library/set/sortedset/superset_spec.rb
new file mode 100644
index 0000000000..a1bbacb966
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/superset_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#superset?" do
+    before :each do
+      @set = SortedSet[1, 2, 3, 4]
+    end
+
+    it "returns true if passed a SortedSet that equals self or self is a proper superset of" do
+      @set.superset?(@set).should be_true
+      SortedSet[].superset?(SortedSet[]).should be_true
+
+      @set.superset?(SortedSet[]).should be_true
+      SortedSet[1, 2, 3].superset?(SortedSet[]).should be_true
+      SortedSet["a", "b", "c"].superset?(SortedSet[]).should be_true
+
+      @set.superset?(SortedSet[1, 2, 3]).should be_true
+      @set.superset?(SortedSet[1, 3]).should be_true
+      @set.superset?(SortedSet[1, 2]).should be_true
+      @set.superset?(SortedSet[1]).should be_true
+
+      @set.superset?(SortedSet[5]).should be_false
+      @set.superset?(SortedSet[1, 5]).should be_false
+      @set.superset?(SortedSet["test"]).should be_false
+    end
+
+    it "raises an ArgumentError when passed a non-SortedSet" do
+      -> { SortedSet[].superset?([]) }.should raise_error(ArgumentError)
+      -> { SortedSet[].superset?(1) }.should raise_error(ArgumentError)
+      -> { SortedSet[].superset?("test") }.should raise_error(ArgumentError)
+      -> { SortedSet[].superset?(Object.new) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/to_a_spec.rb b/spec/ruby/library/set/sortedset/to_a_spec.rb
new file mode 100644
index 0000000000..bb54cd7cdb
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/to_a_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require 'set'
+
+  describe "SortedSet#to_a" do
+    it "returns an array containing elements" do
+      set = SortedSet.new [1, 2, 3]
+      set.to_a.should == [1, 2, 3]
+    end
+
+    it "returns a sorted array containing elements" do
+      set = SortedSet[2, 3, 1]
+      set.to_a.should == [1, 2, 3]
+
+      set = SortedSet.new [5, 6, 4, 4]
+      set.to_a.should == [4, 5, 6]
+    end
+  end
+end
diff --git a/spec/ruby/library/set/sortedset/union_spec.rb b/spec/ruby/library/set/sortedset/union_spec.rb
new file mode 100644
index 0000000000..c942f20d3e
--- /dev/null
+++ b/spec/ruby/library/set/sortedset/union_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is ""..."3.0" do
+  require_relative 'shared/union'
+  require 'set'
+
+  describe "SortedSet#union" do
+    it_behaves_like :sorted_set_union, :union
+  end
+
+  describe "SortedSet#|" do
+    it_behaves_like :sorted_set_union, :|
+  end
+end
diff --git a/spec/ruby/library/set/subset_spec.rb b/spec/ruby/library/set/subset_spec.rb
new file mode 100644
index 0000000000..f375efa6df
--- /dev/null
+++ b/spec/ruby/library/set/subset_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#subset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that is equal to self or self is a subset of" do
+    @set.subset?(@set).should be_true
+    Set[].subset?(Set[]).should be_true
+
+    Set[].subset?(@set).should be_true
+    Set[].subset?(Set[1, 2, 3]).should be_true
+    Set[].subset?(Set["a", :b, ?c]).should be_true
+
+    Set[1, 2, 3].subset?(@set).should be_true
+    Set[1, 3].subset?(@set).should be_true
+    Set[1, 2].subset?(@set).should be_true
+    Set[1].subset?(@set).should be_true
+
+    Set[5].subset?(@set).should be_false
+    Set[1, 5].subset?(@set).should be_false
+    Set[nil].subset?(@set).should be_false
+    Set["test"].subset?(@set).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].subset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].subset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].subset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].subset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true if passed a Set-like object that self is a subset of" do
+      Set[1, 2, 3].subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/set/subtract_spec.rb b/spec/ruby/library/set/subtract_spec.rb
new file mode 100644
index 0000000000..56713de8b3
--- /dev/null
+++ b/spec/ruby/library/set/subtract_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#subtract" do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "deletes any elements contained in other and returns self" do
+    @set.subtract(Set[:b, :c]).should == @set
+    @set.should == Set[:a]
+  end
+
+  it "accepts any enumerable as other" do
+    @set.subtract([:c]).should == Set[:a, :b]
+  end
+end
diff --git a/spec/ruby/library/set/superset_spec.rb b/spec/ruby/library/set/superset_spec.rb
new file mode 100644
index 0000000000..bd9d2f3eee
--- /dev/null
+++ b/spec/ruby/library/set/superset_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+require 'set'
+
+describe "Set#superset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that equals self or self is a proper superset of" do
+    @set.superset?(@set).should be_true
+    Set[].superset?(Set[]).should be_true
+
+    @set.superset?(Set[]).should be_true
+    Set[1, 2, 3].superset?(Set[]).should be_true
+    Set["a", :b, ?c].superset?(Set[]).should be_true
+
+    @set.superset?(Set[1, 2, 3]).should be_true
+    @set.superset?(Set[1, 3]).should be_true
+    @set.superset?(Set[1, 2]).should be_true
+    @set.superset?(Set[1]).should be_true
+
+    @set.superset?(Set[5]).should be_false
+    @set.superset?(Set[1, 5]).should be_false
+    @set.superset?(Set[nil]).should be_false
+    @set.superset?(Set["test"]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].superset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].superset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].superset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].superset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true if passed a Set-like object that self is a superset of" do
+      Set[1, 2, 3, 4].superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/set/to_a_spec.rb b/spec/ruby/library/set/to_a_spec.rb
new file mode 100644
index 0000000000..689e44f38a
--- /dev/null
+++ b/spec/ruby/library/set/to_a_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require 'set'
+
+describe "Set#to_a" do
+  it "returns an array containing elements of self" do
+    Set[1, 2, 3].to_a.sort.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/library/set/to_s_spec.rb b/spec/ruby/library/set/to_s_spec.rb
new file mode 100644
index 0000000000..7b9f7b6603
--- /dev/null
+++ b/spec/ruby/library/set/to_s_spec.rb
@@ -0,0 +1,11 @@
+require_relative 'shared/inspect'
+require 'set'
+
+describe "Set#to_s" do
+  it_behaves_like :set_inspect, :to_s
+
+  it "is an alias of inspect" do
+    set = Set.new
+    set.method(:to_s).should == set.method(:inspect)
+  end
+end
diff --git a/spec/ruby/library/set/union_spec.rb b/spec/ruby/library/set/union_spec.rb
new file mode 100644
index 0000000000..20fe0ddca3
--- /dev/null
+++ b/spec/ruby/library/set/union_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require_relative 'shared/union'
+require 'set'
+
+describe "Set#union" do
+  it_behaves_like :set_union, :union
+end
+
+describe "Set#|" do
+  it_behaves_like :set_union, :|
+end