Ensure Hash#except is allowed on a frozen hash. References #382

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

activesupport/lib/active_support/core_ext/hash/except.rb

@@ -10,7 +10,7 @@ module Hash #:nodoc:
       module Except
         # Returns a new hash without the given keys.
         def except(*keys)
-          clone.except!(*keys)
+          dup.except!(*keys)
         end
 
         # Replaces the hash without the given keys.

activesupport/test/core_ext/hash_ext_test.rb

@@ -341,6 +341,20 @@ def test_except
     assert_equal expected, original.except!(:c)
     assert_equal expected, original
   end
+
+  def test_except_with_original_frozen
+    original = { :a => 'x', :b => 'y' }
+    original.freeze
+    assert_nothing_raised { original.except(:a) }
+  end
+
+  uses_mocha 'except with expectation' do
+    def test_except_with_mocha_expectation_on_original
+      original = { :a => 'x', :b => 'y' }
+      original.expects(:delete).never
+      original.except(:a)
+    end
+  end
 end
 
 class IWriteMyOwnXML