Exercise 2: A Corrected Integration Test — Possible Solution
====================================================================

THE FIX
------------------------------
    class UserRegistrationServiceFixed:
        def __init__(self, sender):
            self.sender = sender
            self.users = []
        def register(self, email):
            self.users.append(email)
            self.sender.send(email, "Welcome!", "Thanks for signing up!")  # matches the new 3-arg signature
            return {'email': email, 'registered': True}

    def test_registration_integration_fixed():
        real_sender = RealNotificationSenderV2()
        service = UserRegistrationServiceFixed(real_sender)
        result = service.register("frank@example.com")
        assert service.users == ["frank@example.com"]
        assert result['registered'] is True
        return True

RESULT
------------------------------
    Integration test against RealNotificationSenderV2: PASS

The integration test now passes cleanly against the real dependency,
confirming the fix rather than merely detecting the original break.

WHY THIS WORKS AS AN ANSWER
------------------------------
This closes the loop the chapter opened: an integration test caught
the original bug by wiring the real seam together; the same kind of
test, run again after the fix, is what actually proves the fix worked
- not just that the code compiles, but that the real, unmocked
dependency accepts the call without error. This is the same discipline
Clean Code, SOLID & Refactoring's own capstone used throughout its
own six-step refactor: verify the bug exists with a real reproduction,
then verify the same reproduction now succeeds after the fix, using
the identical check both times.