def test_ntl_first(self): self.assertEqual(etao.num_to_letter(1), 'A')
def test_ntl_invalid_index_after(self): with self.assertRaises(ValueError): etao.num_to_letter(27)
def test_ntl_invalid_type(self): with self.assertRaises(TypeError): etao.num_to_letter('A')
def test_ntl_last(self): self.assertEqual(etao.num_to_letter(26), 'Z')