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diff --git a/spec/ruby/core/hash/merge_spec.rb b/spec/ruby/core/hash/merge_spec.rb
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+++ b/spec/ruby/core/hash/merge_spec.rb
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+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Hash#merge" do
+  it "returns a new hash by combining self with the contents of other" do
+    h = { 1 => :a, 2 => :b, 3 => :c }.merge(a: 1, c: 2)
+    h.should == { c: 2, 1 => :a, 2 => :b, a: 1, 3 => :c }
+
+    hash = { a: 1, b: 2 }
+    {}.merge(hash).should == hash
+    hash.merge({}).should == hash
+
+    h = { 1 => :a, 2 => :b, 3 => :c }.merge(1 => :b)
+    h.should == { 1 => :b, 2 => :b, 3 => :c }
+
+    h = { 1 => :a, 2 => :b }.merge(1 => :b, 3 => :c)
+    h.should == { 1 => :b, 2 => :b, 3 => :c }
+  end
+
+  it "sets any duplicate key to the value of block if passed a block" do
+    h1 = { a: 2, b: 1, d: 5 }
+    h2 = { a: -2, b: 4, c: -3 }
+    r = h1.merge(h2) { |k,x,y| nil }
+    r.should == { a: nil, b: nil, c: -3, d: 5 }
+
+    r = h1.merge(h2) { |k,x,y| "#{k}:#{x+2*y}" }
+    r.should == { a: "a:-2", b: "b:9", c: -3, d: 5 }
+
+    -> {
+      h1.merge(h2) { |k, x, y| raise(IndexError) }
+    }.should.raise(IndexError)
+
+    r = h1.merge(h1) { |k,x,y| :x }
+    r.should == { a: :x, b: :x, d: :x }
+  end
+
+  it "tries to convert the passed argument to a hash using #to_hash" do
+    obj = mock('{1=>2}')
+    obj.should_receive(:to_hash).and_return({ 1 => 2 })
+    { 3 => 4 }.merge(obj).should == { 1 => 2, 3 => 4 }
+  end
+
+  it "does not call to_hash on hash subclasses" do
+    { 3 => 4 }.merge(HashSpecs::ToHashHash[1 => 2]).should == { 1 => 2, 3 => 4 }
+  end
+
+  it "returns subclass instance for subclasses" do
+    HashSpecs::MyHash[1 => 2, 3 => 4].merge({ 1 => 2 }).should.instance_of?(HashSpecs::MyHash)
+    HashSpecs::MyHash[].merge({ 1 => 2 }).should.instance_of?(HashSpecs::MyHash)
+
+    { 1 => 2, 3 => 4 }.merge(HashSpecs::MyHash[1 => 2]).class.should == Hash
+    {}.merge(HashSpecs::MyHash[1 => 2]).class.should == Hash
+  end
+
+  it "processes entries with same order as each()" do
+    h = { 1 => 2, 3 => 4, 5 => 6, "x" => nil, nil => 5, [] => [] }
+    merge_pairs = []
+    each_pairs = []
+    h.each_pair { |k, v| each_pairs << [k, v] }
+    h.merge(h) { |k, v1, v2| merge_pairs << [k, v1] }
+    merge_pairs.should == each_pairs
+  end
+
+  it "preserves the order of merged elements" do
+    h1 = { 1 => 2, 3 => 4, 5 => 6 }
+    h2 = { 1 => 7 }
+    merge_pairs = []
+    h1.merge(h2).each_pair { |k, v| merge_pairs << [k, v] }
+    merge_pairs.should == [[1,7], [3, 4], [5, 6]]
+  end
+
+  it "preserves the order of merged elements for large hashes" do
+    h1 = {}
+    h2 = {}
+    merge_pairs = []
+    expected_pairs = []
+    (1..100).each { |x| h1[x] = x; h2[101 - x] = x; expected_pairs << [x, 101 - x] }
+    h1.merge(h2).each_pair { |k, v| merge_pairs << [k, v] }
+    merge_pairs.should == expected_pairs
+  end
+
+  it "accepts multiple hashes" do
+    result = { a: 1 }.merge({ b: 2 }, { c: 3 }, { d: 4 })
+    result.should == { a: 1, b: 2, c: 3, d: 4 }
+  end
+
+  it "accepts zero arguments and returns a copy of self" do
+    hash = { a: 1 }
+    merged = hash.merge
+
+    merged.should.eql?(hash)
+    merged.should_not.equal?(hash)
+  end
+
+  it "retains the default value" do
+    h = Hash.new(1)
+    h.merge(b: 1, d: 2).default.should == 1
+  end
+
+  it "retains the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.merge(b: 1, d: 2).default_proc.should == pr
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.merge(b: 1, d: 2)
+    h2.compare_by_identity?.should == true
+  end
+
+  it "ignores compare_by_identity flag of an argument" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = { b: 1, d: 2 }.merge(h)
+    h2.compare_by_identity?.should == false
+  end
+end
+
+describe "Hash#merge!" do
+  it "is an alias of Hash#update" do
+    Hash.instance_method(:merge!).should == Hash.instance_method(:update)
+  end
+end