def test_empty(self): self.assertEqual(sum_of_digits(''), 0)
def test_double_digits(self): self.assertEqual(sum_of_digits('82'), 10)
def test_triple_digits(self): self.assertEqual(sum_of_digits('123'), 6)
def test_10(self): self.assertEqual(sum_of_digits('1234'), 10)
def test_single_digit(self): self.assertEqual(sum_of_digits('9'), 9)
def test_4(self): self.assertEqual(sum_of_digits('1111'), 4)
def test_0(self): self.assertEqual(sum_of_digits(''), 0)
def test_11(self): self.assertEqual(sum_of_digits('434'), 11)