如何模拟 class 实例并使用 mocker.patch.object() 和 pytest-mock 为该实例分配属性？

Question

I am trying to unit test a module (using pytest and pytest-mock) and I would like to create a mocked instance of a class with certain values for its attributes to be used in a @pytest.fixture

I think I've finally found what I'm looking for in patch.object and autospeccing but I don't understand what the arguments are supposed to be, specifically 'attribute'

patch.object(target, attribute, new=DEFAULT, spec=None, create=False,
spec_set=None, autospec=None, new_callable=None, **kwargs)

patch the named member (attribute) on an object (target) with a mock object.

I tried searching for patch.object() examples but I'm only seeing use cases related to mocking the return values for methods in a class.

Like in this example, a method is passed as the 'attribute' argument to patch.object().

Any help or hints in the right direction would be greatly appreciated!

Answer 1

An example would be the method that you're trying to test.

So, if I wanted to check to see if MyClass.method_a was called, I would do:

from .functions import MyClass  # import MyClass from wherever 
                                # it is used in the module.


with patch.object(MyClass, 'method_a') as mocked_myclass:
    function_that_called_myclass_method_a()

mocked_myclass.assert_called()