Safer restoration of stubbed method visibility. Fixes #141.

It is possible for `Module#public`, `#protected` and `#private` to be
redefined on descendant classes, so it' safer to use the original
version of these methods on `Module` when restoring the visibility of
stubbed methods.

Rather than add a completely new set of tests for these scenarios, I
have just embellished the existing tests. It's not ideal, because it
makes it less clear what's going on, but I think it'll do.

lib/mocha/any_instance_method.rb

@@ -46,7 +46,7 @@ def remove_new_method
     def restore_original_method
       if @original_method && @original_method.owner == stubbee
         stubbee.send(:define_method, method, @original_method)
-        stubbee.send(@original_visibility, method)
+        Module.instance_method(@original_visibility).bind(stubbee).call(method)
       end
     end
 

lib/mocha/class_method.rb

@@ -77,7 +77,7 @@ def restore_original_method
         end
       end
       if @original_visibility
-        stubbee.__metaclass__.send(@original_visibility, method)
+        Module.instance_method(@original_visibility).bind(stubbee.__metaclass__).call(method)
       end
     end
 

test/acceptance/stub_any_instance_method_test.rb

@@ -32,6 +32,8 @@ def test_should_leave_stubbed_public_method_unchanged_after_test
       def my_instance_method
         :original_return_value
       end
+      public :my_instance_method
+      def self.public(*args); end
     end
     instance = klass.new
     run_as_test do
@@ -47,6 +49,7 @@ def my_instance_method
         :original_return_value
       end
       protected :my_instance_method
+      def self.protected(*args); end
       def my_unprotected_instance_method
         my_instance_method
       end
@@ -65,6 +68,7 @@ def my_instance_method
         :original_return_value
       end
       private :my_instance_method
+      def self.private(*args); end
     end
     instance = klass.new
     run_as_test do

test/acceptance/stub_class_method_defined_on_class_test.rb

@@ -20,6 +20,7 @@ def my_class_method
           :original_return_value
         end
         public :my_class_method
+        def self.public(*args); end
       end
     end
     assert_snapshot_unchanged(klass) do
@@ -39,6 +40,7 @@ def my_class_method
           :original_return_value
         end
         protected :my_class_method
+        def self.protected(*args); end
       end
     end
     assert_snapshot_unchanged(klass) do
@@ -58,6 +60,7 @@ def my_class_method
           :original_return_value
         end
         private :my_class_method
+        def self.private(*args); end
       end
     end
     assert_snapshot_unchanged(klass) do