1 files changed, 110 insertions, 0 deletions
diff --git a/spec/ruby/core/hash/transform_keys_spec.rb b/spec/ruby/core/hash/transform_keys_spec.rb
new file mode 100644
index 0000000000..379638bd4b
--- /dev/null
+++ b/spec/ruby/core/hash/transform_keys_spec.rb
@@ -0,0 +1,110 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+ruby_version_is "2.5" do
+  describe "Hash#transform_keys" do
+    before :each do
+      @hash = { a: 1, b: 2, c: 3 }
+    end
+
+    it "returns new hash" do
+      ret = @hash.transform_keys(&:succ)
+      ret.should_not equal(@hash)
+      ret.should be_an_instance_of(Hash)
+    end
+
+    it "sets the result as transformed keys with the given block" do
+      @hash.transform_keys(&:succ).should ==  { b: 1, c: 2, d: 3 }
+    end
+
+    it "keeps last pair if new keys conflict" do
+      @hash.transform_keys { |_| :a }.should == { a: 3 }
+    end
+
+    it "makes both hashes to share values" do
+      value = [1, 2, 3]
+      new_hash = { a: value }.transform_keys(&:upcase)
+      new_hash[:A].should equal(value)
+    end
+
+    context "when no block is given" do
+      it "returns a sized Enumerator" do
+        enumerator = @hash.transform_keys
+        enumerator.should be_an_instance_of(Enumerator)
+        enumerator.size.should == @hash.size
+        enumerator.each(&:succ).should == { b: 1, c: 2, d: 3 }
+      end
+    end
+
+    it "returns a Hash instance, even on subclasses" do
+      klass = Class.new(Hash)
+      h = klass.new
+      h[:foo] = 42
+      r = h.transform_keys{|v| :"x#{v}"}
+      r.keys.should == [:xfoo]
+      r.class.should == Hash
+    end
+  end
+
+  describe "Hash#transform_keys!" do
+    before :each do
+      @hash = { a: 1, b: 2, c: 3, d: 4 }
+      @initial_pairs = @hash.dup
+    end
+
+    it "returns self" do
+      @hash.transform_keys!(&:succ).should equal(@hash)
+    end
+
+    it "updates self as transformed values with the given block" do
+      @hash.transform_keys!(&:to_s)
+      @hash.should == { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4 }
+    end
+
+    it "does not prevent conflicts between new keys and old ones" do
+      @hash.transform_keys!(&:succ)
+      @hash.should == { e: 1 }
+    end
+
+    it "partially modifies the contents if we broke from the block" do
+      @hash.transform_keys! do |v|
+        break if v == :c
+        v.succ
+      end
+      @hash.should == { c: 1, d: 4 }
+    end
+
+    it "keeps later pair if new keys conflict" do
+      @hash.transform_keys! { |_| :a }.should == { a: 4 }
+    end
+
+    context "when no block is given" do
+      it "returns a sized Enumerator" do
+        enumerator = @hash.transform_keys!
+        enumerator.should be_an_instance_of(Enumerator)
+        enumerator.size.should == @hash.size
+        enumerator.each(&:upcase).should == { A: 1, B: 2, C: 3, D: 4 }
+      end
+    end
+
+    describe "on frozen instance" do
+      before :each do
+        @hash.freeze
+      end
+
+      it "raises a RuntimeError on an empty hash" do
+        ->{ {}.freeze.transform_keys!(&:upcase) }.should raise_error(RuntimeError)
+      end
+
+      it "keeps pairs and raises a RuntimeError" do
+        ->{ @hash.transform_keys!(&:upcase) }.should raise_error(RuntimeError)
+        @hash.should == @initial_pairs
+      end
+
+      context "when no block is given" do
+        it "does not raise an exception" do
+          @hash.transform_keys!.should be_an_instance_of(Enumerator)
+        end
+      end
+    end
+  end
+end