python单元测试断言用部分调用

Question

using python 3.5.3 I want to assert that mocked function received specific arguments, but I don't want to check all received arguments, only the ones which are important for the test.

for example, instead of doing that:

my_func_mock.assert_called_with('arg1','arg2','arg3')

I would like to do something like:

my_func_mock.assert_called_with_partial(arg2='arg2')

Is it possible?

Answer 1

assert_called_with checks how the last call is made. In a MagicMock object, the last call's args can be found in its call_args.args attribute. The last call's kwargs can be found in its call_args.kwargs attribute. We can check these individually.

Say in a test we have called my_func_mock with

my_func_mock(arg0, arg1, kwarg1 = 'kw1', kwarg2 = 'kw2')

We can directly check individual args by

assert my_func_mock.call_args.args[0] == arg0
assert my_func_mock.call_args.args[1] == arg1

and for any kwargs, we can directly check them individually by

assert my_func_mock.call_args.kwargs['kwarg1'] == 'kw1'
assert my_func_mock.call_args.kwargs['kwarg2'] == 'kw2'

Answer 2

You can copy the source of mock.NonCallableMock.assert_called_with and modify it so that you can implement the following assert_called_with_partial that partially matches the expected arguments and keyword arguments:

from unittest import mock

def assert_called_with_partial(_mock_self, *args, **kwargs):
    self = _mock_self
    if self.call_args is None:
        expected = self._format_mock_call_signature(args, kwargs)
        raise AssertionError('Expected call: %s\nNot called' % (expected,))

    def _error_message():
        msg = self._format_mock_failure_message(args, kwargs)
        return msg

    expected = self._call_matcher((args, kwargs))
    expected_args, expected_kwargs = expected
    actual_args, actual_kwargs = self._call_matcher(self.call_args)
    if actual_args[:len(expected_args)] != expected_args or not (expected_kwargs.items() <= actual_kwargs.items()):
        cause = expected if isinstance(expected, Exception) else None
        raise AssertionError(_error_message()) from cause

mock.NonCallableMock.assert_called_with_partial = assert_called_with_partial

so that:

m = mock.MagicMock()
m(1, 2, a=1, b=2)
m.assert_called_with_partial(1, a=1)

will not raise an AssertionError , but:

m.assert_called_with_partial(1, 2, a=2)

will raise:

AssertionError: Expected call: mock(1, 2, a=2)
Actual call: mock(1, 2, a=1, b=2)

Answer 3

You can use ANY from unittest.mock.

from unittest.mock import MagicMock, ANY
my_func_mock = MagicMock()
my_func_mock('argument', 1, foo='keyword argument', bar={'a thing': 2})
my_func_mock.assert_called_once_with(
    'argument',
    1,
    foo='keyword argument',
    bar=ANY
)

This requires knowing the argument names already but allows any value for that argument.

See: https://docs.python.org/3/library/unittest.mock.html#unittest.mock.ANY