Mock is useful when mocking the parameter passed into a specific class during the instantiation of the class. Then you can mock attributes of that parameter, which will be called instead of an actual parameter being passed to the contructor.
In the example below, the gateway is mocked and dummy data is given as the return value for the get_something method of the gateway. In this case, only the get_upper_something is unit tested, while the dependecies are mocked out.
from unittest.mock import Mock
class Service():
def __init__(self, gateway):
self.gateway = gateway
def get_upper_something(self):
return gateway.get_something()
def test_get_upper_something():
gateway = Mock()
gateway.get_something.return_value = [1, 2]
service = Service(gateway)
service.get_upper_something()
assert result == [1, 2]