old_contents: import unittest
  from robber import expect
  from robber.matchers.contain import Contain
  
  class TestAbove(unittest.TestCase):
      def test_matches(self):
          expect(Contain({'key': 'value'}, 'key').matches()) == True
          expect(Contain([1, 2, 3], 2).matches()) == True
          expect(Contain((1, 2, 3), 3).matches()) == True
  
          expect(Contain({'key': 'value'}, 'other').matches()) == False
          expect(Contain([1, 2, 3], 4).matches()) == False
          expect(Contain((1, 2, 3), 4).matches()) == False
  
      def test_failure_message(self):
          contain = Contain([1, 2, 3], 4)
          expect(contain.failure_message()) == 'Expected {0} to contain 4'.format([1, 2, 3])
  
      def test_register(self):
          expect(expect.matcher('contain')) == Contain
  
new_contents: import unittest
  from robber import expect
  from robber.matchers.contain import Contain
  
  class TestContain(unittest.TestCase):
      def test_matches(self):
          expect(Contain({'key': 'value'}, 'key').matches()) == True
          expect(Contain([1, 2, 3], 2).matches()) == True
          expect(Contain((1, 2, 3), 3).matches()) == True
  
          expect(Contain({'key': 'value'}, 'other').matches()) == False
          expect(Contain([1, 2, 3], 4).matches()) == False
          expect(Contain((1, 2, 3), 4).matches()) == False
  
      def test_failure_message(self):
          contain = Contain([1, 2, 3], 4)
          expect(contain.failure_message()) == 'Expected {0} to contain 4'.format([1, 2, 3])
  
      def test_register(self):
          expect(expect.matcher('contain')) == Contain
  
subject: Rename the 'contain' TestCase to TestContain