def test_1_solution(self):
self.assertEqual(quadratic_formula(1, 2, 1), -1.0)
def test_string_fails(self):
with self.assertRaises(TypeError):
quadratic_formula("jan", "piet", "klaas")
def test_2_answers(self):
self.assertEqual(quadratic_formula(1, 5, 6), (-3.0, -2.0))
def test_no_solution(self):
self.assertIsNone(quadratic_formula(1, 0, 16))