A beautiful, elegant test case.

foo_service_test.py

class MyTestCase(unittest.TestCase):

  testFoo_ShouldUpdateBarService_ForUserWithExistingBaz(self):
    # foo calls the Garble service internally, so we mock the response.
    supposeGarbleServiceReturns(EXPECTED_GARBLE_RESPONSE);
    user = makeSimpleUserWithExistingBaz();
  
    foo(user);
  
    # Ensure Bar was updated to contain the recent user.
    self.assertIn(user.id, (u.id for u in bar_service.recentUsers()));