def test_find_index_of_overlap_no_match(self):
     fst_string = 'CCAGTAC'
     snd_string = ''
     assert find_index_of_overlap(fst_string, snd_string) is None
 def test_find_index_of_overlap_one_char(self):
     fst_string = 'CCAGTAC'
     snd_string = 'C'
     assert find_index_of_overlap(fst_string, snd_string) == 6