def test_add_coached_by(self):
one = User(0)
two = User(0)
one.add_coached_by(two)
self.assertIn(two, one.coached_by)
self.assertIn(one, two.coaches)
def test_spread_via_coached_by_relationship(self):
a = User()
b = User()
a.add_coached_by(b)
infected_classrooms = total_infection(a)
self.assertEqual(infected_classrooms.infected, set([a, b]))
