old_contents: import unittest
  
  class TestListComp(unittest.TestCase):
    "Tests of list comprehension"
  
    def test_basic_comp(self):
      all_nums = [x for x in range(1, 1000)]
      for num in all_nums:
        self.assertLess(num, 1000)
    
    def test_multivariate_comp(self):
      sets = [(op1, op2) for op1 in range(1,12) for op2 in range(1, 12)]
      for ops in sets:
        self.assertLess(ops[0] * ops[1], 144)
  
new_contents: import unittest
  
  class TestListComp(unittest.TestCase):
    "Tests of list comprehension"
  
    def test_basic_comp(self):
      all_nums = [x for x in range(1, 1000)]
      for num in all_nums:
        self.assertLess(num, 1000)
    
    def test_multivariate_comp(self):
      sets = [(op1, op2) for op1 in range(1,12) for op2 in range(1, 12)]
      for ops in sets:
        self.assertLess(ops[0] * ops[1], 144)
  
    def test_histogram(self):
      sentence = 'this histogram is historic'
      histogram = {letter: sentence.count(letter) for letter in sentence}
      self.assertEqual(histogram['t'], 3)
  
subject: test histogram