AssertionError "not called" on simple mock in Python

Question

I'm trying to use the Python mock module (downloaded using pip) for the first time. I'm having problems setting an assert, I've narrowed it down to this code:

class TestUsingMock(unittest.TestCase):

    def setUp(self):
        self.fake_client = mock.Mock()

    def test_mock(self):
        self.fake_client.copy = mock.Mock()
        self.fake_client.copy("123")
        self.fake_client.assert_called_with("123")

if __name__ == "__main__":
    unittest.main()

This is the error I get:

F
======================================================================
FAIL: test_mock (__main__.TestVCSDriver)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./mock_test.py", line 17, in test_mock
    self.fake_client.assert_called_with("123")
  File "/Library/Python/2.6/site-packages/mock.py", line 859, in assert_called_with
    raise AssertionError('Expected call: %s\nNot called' % (expected,))
AssertionError: Expected call: mock('123')
Not called

Without the assertion, everything works fine. What am I doing wrong?

Answer 1

You are calling the object self.fake_client.copy, but test whether another one, self.fake_client has been called.

Either call the "correct" object:

self.fake_client("123")
self.fake_client.assert_called_with("123")

or test the copy:

self.fake_client.copy("123")
self.fake_client.copy.assert_called_with("123")