def test_find_common_substring_returns_correct_output_on_valid_input_strings(self):
self.assertEqual(find_common_substring_quadratic('ABCDEF', 'ABCDEFGH'), 'abcdef')
self.assertEqual(find_common_substring_quadratic('SABCDEF', 'FCZ3DRES'), 'scdef')
self.assertEqual(find_common_substring_quadratic('techcrunch', 'the next web'), 'tehnh')
self.assertEqual(find_common_substring_quadratic('Microsoft azure', 'Amazon AWS'), 'mosoaz')
self.assertEqual(find_common_substring_linear('ABCDEF', 'ABCDEFGH'), 'abcdef')
self.assertEqual(find_common_substring_linear('SABCDEF', 'FCZ3DRES'), 'scdef')
self.assertEqual(find_common_substring_linear('techcrunch', 'the next web'), 'tehnh')
self.assertEqual(find_common_substring_quadratic('Microsoft azure', 'Amazon AWS'), 'mosoaz')
def test_find_common_substring_raises_value_error_on_undefined_inputs(self):
with self.assertRaises(ValueError):
find_common_substring_quadratic(None, None)
with self.assertRaises(ValueError):
find_common_substring_linear(None, None)
def test_find_common_substring_returns_empty_string_if_first_string_is_empty(self):
self.assertEqual(find_common_substring_quadratic('', 'string 2'), '')
self.assertEqual(find_common_substring_linear('', 'string 2'), '')
def test_find_common_substring_raises_type_error_on_a_non_string_type(self):
with self.assertRaises(TypeError):
find_common_substring_quadratic({}, 1234)
with self.assertRaises(TypeError):
find_common_substring_linear({}, 1234)