Mocking in Python just got easier

Voidspace just released Mock 0.4.0 – an update to the excellent Mock library which brings a few conveniences and easier patching of module and class-level attributes.

This makes tests using mocks easier to read, for example inside a test case:

self.assertEquals(my_mock.my_method.call_args,     (('goodbye',),{'hello': False}))

Can now be written as:
my_mock.my_method.assert_called_with('goodbye', hello=False)

Check it out!

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Written by Michael

October 14, 2008 at 6:31 am

Posted in python, testing

2 Responses

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You should check out chai, it makes it even easier http://pypi.python.org/pypi/chai#example

Vitaly babiy

June 21, 2011 at 8:48 pm

Reply

Hi Vitaly! Just to make the comparison obvious, the contrived example of mocking a particular method on an object looks like this with Chai:

        obj = CustomObject()
        self.expect(obj.get).args('name').returns('My Name')
        self.assert_equals(obj.get('name'), 'My Name')

while the mock way looks like:

        obj = CustomObject()
        with patch.object(obj, 'get') as mock_get:
                mock_get.return_value = 'My Name'
                self.assertEqual(obj.get('name'), 'My Name')

In a real example, the mock version would probably look more like this:

        mock_obj = Mock(spec=CustomObject)
        
        # Make the call that should result in calling the get method.
        
        mock_obj.get.assert_called_with('name')
        self.assertEqual(returned_name_from_actual_call, mock_object.get.return_value)

Maybe it’s just because I’m used to it, but in both examples I personally find the mock version easier (ie. I don’t have to specify the return value to know that the correct value was received and returned by my calling function, and assert_called_with is just so easy to read).

Michael

June 22, 2011 at 9:01 am

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