1 files changed, 72 insertions, 0 deletions
diff --git a/test/psych/test_merge_keys.rb b/test/psych/test_merge_keys.rb
new file mode 100644
index 0000000000..fef8892727
--- /dev/null
+++ b/test/psych/test_merge_keys.rb
@@ -0,0 +1,72 @@
+require_relative 'helper'
+
+module Psych
+  class TestMergeKeys < TestCase
+    # [ruby-core:34679]
+    def test_merge_key
+      yaml = <<-eoyml
+foo: &foo
+  hello: world
+bar:
+  << : *foo
+  baz: boo
+      eoyml
+
+      hash = {
+        "foo" => { "hello" => "world"},
+        "bar" => { "hello" => "world", "baz" => "boo" } }
+      assert_equal hash, Psych.load(yaml)
+    end
+
+    def test_multiple_maps
+      yaml = <<-eoyaml
+---
+- &CENTER { x: 1, y: 2 }
+- &LEFT { x: 0, y: 2 }
+- &BIG { r: 10 }
+- &SMALL { r: 1 }
+
+# All the following maps are equal:
+
+- # Merge multiple maps
+  << : [ *CENTER, *BIG ]
+  label: center/big
+      eoyaml
+
+      hash = {
+        'x' => 1,
+        'y' => 2,
+        'r' => 10,
+        'label' => 'center/big'
+      }
+
+      assert_equal hash, Psych.load(yaml)[4]
+    end
+
+    def test_override
+      yaml = <<-eoyaml
+---
+- &CENTER { x: 1, y: 2 }
+- &LEFT { x: 0, y: 2 }
+- &BIG { r: 10 }
+- &SMALL { r: 1 }
+
+# All the following maps are equal:
+
+- # Override
+  << : [ *BIG, *LEFT, *SMALL ]
+  x: 1
+  label: center/big
+      eoyaml
+
+      hash = {
+        'x' => 1,
+        'y' => 2,
+        'r' => 10,
+        'label' => 'center/big'
+      }
+
+      assert_equal hash, Psych.load(yaml)[4]
+    end
+  end
+end