def test_twelve_hour_clock_with_length_of_four(self):
self.assertEquals(hour_format('12am'), '00:00:00')
self.assertEquals(hour_format('12pm'), '12:00:00')
self.assertEquals(hour_format('03pm'), '15:00:00')
def test_two_letter_string(self):
self.assertEquals(hour_format('12'), '12:00:00')
def test_twelve_hour_clock_with_length_of_three(self):
self.assertEquals(hour_format('1am'), '01:00:00')
self.assertEquals(hour_format('1pm'), '13:00:00')
def test_one_letter_string(self):
self.assertEquals(hour_format('0'), '00:00:00')
