1 files changed, 51 insertions, 0 deletions
diff --git a/spec/ruby/core/hash/hash_spec.rb b/spec/ruby/core/hash/hash_spec.rb
new file mode 100644
index 0000000000..cd67f7a652
--- /dev/null
+++ b/spec/ruby/core/hash/hash_spec.rb
@@ -0,0 +1,51 @@
+require_relative '../../spec_helper'
+
+describe "Hash" do
+  it "includes Enumerable" do
+    Hash.include?(Enumerable).should == true
+  end
+end
+
+describe "Hash#hash" do
+  it "returns a value which doesn't depend on the hash order" do
+    { 0=>2, 11=>1 }.hash.should == { 11=>1, 0=>2 }.hash
+  end
+
+  it "returns a value in which element values do not cancel each other out" do
+    { a: 2, b: 2 }.hash.should_not == { a: 7, b: 7 }.hash
+  end
+
+  it "returns a value in which element keys and values do not cancel each other out" do
+    { :a => :a }.hash.should_not == { :b => :b }.hash
+  end
+
+  it "generates a hash for recursive hash structures" do
+    h = {}
+    h[:a] = h
+    (h.hash == h[:a].hash).should == true
+  end
+
+  it "returns the same hash for recursive hashes" do
+    h = {} ; h[:x] = h
+    h.hash.should == {x: h}.hash
+    h.hash.should == {x: {x: h}}.hash
+    # This is because h.eql?(x: h)
+    # Remember that if two objects are eql?
+    # then the need to have the same hash.
+    # Check the Hash#eql? specs!
+  end
+
+  it "returns the same hash for recursive hashes through arrays" do
+    h = {} ; rec = [h] ; h[:x] = rec
+    h.hash.should == {x: rec}.hash
+    h.hash.should == {x: [h]}.hash
+    # Like above, because h.eql?(x: [h])
+  end
+
+  it "allows omitting values" do
+    a = 1
+    b = 2
+
+    {a:, b:}.should == { a: 1, b: 2 }
+  end
+end