def test_shift_letter_full(self): self.assertEqual(etao.caesar_shift_letter('A', 26), 'A')
def test_shift_letter_invalid_negative(self): with self.assertRaises(ValueError): etao.caesar_shift_letter('A', -1)
def test_shift_letter_max(self): self.assertEqual(etao.caesar_shift_letter('A', 25), 'Z')
def test_shift_letter_none(self): self.assertEqual(etao.caesar_shift_letter('A', 0), 'A')
def test_shift_letter_negative(self): self.assertEqual(etao.caesar_shift_letter('A', -1), 'Z')
def test_shift_letter_min(self): self.assertEqual(etao.caesar_shift_letter('A', 1), 'B')