def test_add_before_a_in_abc(self):
pl = PositionalList()
a = pl.add_last('a')
b = pl.add_last('b')
c = pl.add_last('c')
forty_two = pl.add_before(a, 42)
actual_before_forty_two = pl.before(forty_two)
self.assertIsNone(actual_before_forty_two)
def test_add_before_b_in_abc(self):
pl = PositionalList()
a = pl.add_last('a')
b = pl.add_last('b')
c = pl.add_last('c')
forty_two = pl.add_before(b, 42)
expected_before_forty_two = a
actual_before_forty_two = pl.before(forty_two)
self.assertEqual(expected_before_forty_two, actual_before_forty_two)