Unit test: How to assert multiple calls of same method?

Question

I have a method, which calls another method twice, with different arguments.

class A(object):
    def helper(self, arg_one, arg_two):
        """Return something which depends on arguments."""

    def caller(self):
        value_1 = self.helper(foo, bar)  # First call.
        value_2 = self.helper(foo_bar, bar_foo)  # Second call!

Using assert_called_with helps me asserting just the first call, and not the second one. Even assert_called_once_with doesn't seem to be helpful. What am I missing here? Is there any way to test such calls?

Simeon Visser · Accepted Answer · 2017-03-04 22:08:59Z

19

You can use mock_calls which contains all calls made to a method. This list contains the first call, the second call and all subsequent calls as well. So you can write assertions with mock_calls[1] to state something about the second call.

For example, if m = mock.Mock() and the code does m.method(123) then you write:

assert m.method.mock_calls == [mock.call(123)]

which asserts that the list of calls to m.method is exactly one call, namely a call with the argument 123.

edited Mar 4, 2017 at 22:08

answered Nov 28, 2013 at 16:34

Simeon Visser

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2 Comments

byxor Over a year ago

The example in their documentation doesn't make very much sense. Could you show a better example?

Simeon Visser Over a year ago

@BrandonIbbotson I have added an example to my answer above.

Marcus Lind · Accepted Answer · 2017-10-05 10:12:25Z

4

To add to Simon Visser's answer, you can use the unittest.TestCase self.assertEqual() method instead of the assert syntax, which I'd say is a better practise in the Unit Test context since you can also add comments to it that will be displayed whenever something goes wrong.

So for example:

self.assertEqual(
    [
        mock.call(1, 'ValueA', True)),
        mock.call(2, 'ValueB', False)),
        mock.call(3, 'ValueC', False))
    ],
    mock_cur.execute.mock_calls,
    "The method was not called with the correct arguments."
)

answered Oct 5, 2017 at 10:12

Marcus Lind

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