mocking - How to call self in a mock method of an object in Python?

Question

I try to test some codes which don't return anything but save the result to the DB. By mocking the save method, I wish to check whether things have been processed correctly:

def mock_save(self):
    assert(self.attr, 'dest_val')
with mock.patch.object(Item, "save", create=True) as save:
    save.side_effect = mock_save
    func_to_call() //in func_to_call, I call item.save()

However, it seems that this is not allowed. It says that the number of argument mismatch.

If I do def mock_save(), it won't work.

How can I have a reference to the object which the mock method act upon too? (I saw it in another thread that is applicable to __init__ method which can be called directly from the class).

Answer 1

You need autospec=True

def mock_save(self):
    assert self.attr == 'dest_val'
with mock.patch.object(Item, "save", autospec=True) as save:
    save.side_effect = mock_save
    func_to_call()