Add koans addressing passing a block to Hash#initialize.

koans/about_hashes.rb

@@ -77,4 +77,28 @@ def test_default_value
     assert_equal __, hash2[:one]
     assert_equal __, hash2[:two]
   end
+
+  def test_default_value_is_the_same_object
+    hash = Hash.new([])
+
+    hash[:one] << "uno"
+    hash[:two] << "dos"
+
+    assert_equal __, hash[:one]
+    assert_equal __, hash[:two]
+    assert_equal __, hash[:three]
+
+    assert_equal __, hash[:one].object_id == hash[:two].object_id
+  end
+
+  def test_default_value_with_block
+    hash = Hash.new {|hash, key| hash[key] = [] }
+
+    hash[:one] << "uno"
+    hash[:two] << "dos"
+
+    assert_equal __, hash[:one]
+    assert_equal __, hash[:two]
+    assert_equal __, hash[:three]
+  end
 end