def test_no_text(self):
# arrange
text = ""
# act
result = sort_letters(text)
# assert
self.assertEqual("", result)
def test_handles_capitals(self):
# arrrange
text = "HHeEgg"
# act
result = sort_letters(text)
# assert
self.assertEqual("HHggeE", result)
def test_sort_letters_some_appear_multiple(self):
# arrange
text = "tree"
# act
result = sort_letters(text)
# assert
self.assertEqual("eetr", result)
def test_all_appear_multiple(self):
# arrange
text = "cccaaa"
# act
result = sort_letters(text)
# assert
self.assertEqual("cccaaa", result)
def test_sort_letters_all_occur_once(self):
# arrange
text = "abcde"
# act
result = sort_letters(text)
# assert
self.assertEqual("abcde", result)
