Passing arguments to mock method

Question

I'm brand new to unit testing and mock. I would like to have a mock method append to a dictionary, but I'm not sure how I can accomplish this. I need to pass key and value arguments to append_dict . Using this, I get

SyntaxError: can't assign to function call

Code:

def mock_client(dictionary):
    client = mock.MagicMock()
    client.dictionary = dictionary
    client.append_dictionary(key, value) = client.dictionary[key] = value #this line doesn't work
    return client

The function is called in the file I want to test like so:

client.append_dictionary(key, value)

Answer 1

You could write the method directly and set it to the client object:

def mock_client(dictionary):
    client = mock.MagicMock()
    client.dictionary = dictionary

    def append_dictionary(self, key, value):
        self.dictionary[key] = value

    client.append_dictionary = append_dictionary
    return client

On the other hand, if you wish to test whether append_dictionary is called properly in your code it may be better to do something like this:

mocked_client = mock_client({})
my_code(mocked_client)
self.assertEqual(
    mocked_client.append_dictionary.call_args_list,
    [
        mock.call("key", "value"),
    ]
)