def test_clean_date_empty_string(self):
"""Test clean_date with empty string as input."""
actual_output = CHATCleaner.clean_date('')
desired_output = ''
self.assertEqual(actual_output, desired_output)
def test_clean_date_regular_date(self):
"""Test clean_date with a regular date as input."""
actual_output = CHATCleaner.clean_date('12-SEP-1997')
desired_output = '1997-09-12'
self.assertEqual(actual_output, desired_output)