def test__add__matrix(self) -> None:
        a = Matrix([[1, 2, 3], [2, 4, 5], [6, 7, 8]], 3, 3)
        b = Matrix([[1, 2, 7], [2, 4, 5], [6, 7, 10]], 3, 3)
        self.assertEqual("|2,4,10|\n|4,8,10|\n|12,14,18|\n", str(a + b))