def test_no_roots(self): self.assertIsNone(demo(15, 7, 15))
def test_two_roots_2(self): self.assertEqual(demo(2, 5, 3), (-1.5, -1))
def test_one_root2(self): self.assertEqual(demo(1, 0, 0), 0)
def test_two_roots_1(self): self.assertEqual(demo(1, 0, -1), (-1, 1))