Ошибка математической области

#quadratic_equation.py
from math import sqrt
 
 
def get_roots(a, b, c):
    discriminant = b ** 2 - 4 * a * c
    root1 = (-b - sqrt(discriminant)) / (2 * a)
    root2 = (-b + sqrt(discriminant)) / (2 * a)
    if discriminant == 0:
        return root1, None
    elif discriminant < 0:
        return None, None
    else:
        return root1, root2

#tests.py
import unittest
 
from quadratic_equation import get_roots
 
 
class QuadraticEquationTestCase(unittest.TestCase):
    def test_solves_real_roots(self):
        root1, root2 = get_roots(1, -2, 1)
        self.assertEqual(root1, 1)
 
    def test_first_root_less_than_second(self):
        root1, root2 = get_roots(1, 2, -3)
        self.assertEqual(root1, -3)
        self.assertEqual(root2, 1)
 
    def test_second_root_is_none_if_one_solution(self):
        root1, root2 = get_roots(1, -2, 1)
        self.assertIsNotNone(root1)
        self.assertIsNone(root2)
 
    def test_returns_none_for_complex_solution(self):
        root1, root2 = get_roots(1, 2, 3)
        self.assertIsNone(root1)
        self.assertIsNone(root2)
 
 
if __name__ == '__main__':
    unittest.main()