def test_absent_letter(self):
self.assertEqual(search_start_positions(GRID, 'Q'), [])
def test_more_than_one_possible_positions(self):
self.assertEqual(search_start_positions(GRID, 'A'), [(0, 0), (2, 0)])
self.assertEqual(search_start_positions(GRID, 'C'), [(0, 2), (1, 2)])
self.assertEqual(search_start_positions(GRID, 'E'), [(0, 3), (2, 2), (2, 3)])
def test_positive(self):
self.assertEqual(search_start_positions(GRID, 'F'), [(1, 1)])