How can I unit-test a method without instantiating the class?

Question

I have a class SocketHandler with a method calculate_ticket:

class SocketHandler(A, B, C ..):
    ..

    calculate_ticket(self, key):
        ..
        return ticket

    ..

Now I want to test the method without having to instantiate the class since it is coupled with so many things. Is this possible?

Answer 1

There are several ways using the mock library. One simple way is to mock the instance itself, then call the method using the "long" form.

class ClassToTest(object):
    def __init__(self):
        pass

    def method_to_test(self, y):
        self.x = y
        return 5

fake_instance = mock.Mock()
ClassToTest.__init__(fake_instance)
x = ClassToTest.method_to_test(fake_instance, 3)
assert x == 5
assert fake_instance.x == 3