old_contents: import helper
  from rock import utils
  
  
  class UtilsTestCase(helper.unittest.TestCase):
  
      def test_shell(self):
          utils.Shell.run = lambda self: self
          s = utils.Shell()
          self.assertTrue(isinstance(s.__enter__(), utils.Shell))
          s.write('ok')
          s.__exit__(None, None, None)
          self.assertEqual(s.stdin.getvalue(), 'ok\n')
          def execl(*args):
              self.assertEqual(len(args), 4)
              self.assertEqual(args[0], '/bin/bash')
              self.assertEqual(args[1], '-l')
              self.assertEqual(args[2], '-c')
              self.assertEqual(args[3], 'ok\n')
          utils.os.execl = execl
          s.__exit__('type', 'value', 'tracebook')
  
new_contents: import helper
  from rock import utils
  from rock.exceptions import ConfigError
  
  
  class UtilsTestCase(helper.unittest.TestCase):
  
      def test_shell(self):
          utils.Shell.run = lambda self: self
          s = utils.Shell()
          self.assertTrue(isinstance(s.__enter__(), utils.Shell))
          s.write('ok')
          s.__exit__(None, None, None)
          self.assertEqual(s.stdin.getvalue(), 'ok\n')
          def execl(*args):
              self.assertEqual(len(args), 4)
              self.assertEqual(args[0], '/bin/bash')
              self.assertEqual(args[1], '-l')
              self.assertEqual(args[2], '-c')
              self.assertEqual(args[3], 'ok\n')
          utils.os.execl = execl
          s.__exit__('type', 'value', 'tracebook')
  
      def test_noshell(self):
          utils.ROCK_SHELL = '/tmp/hopefully-no-exists'
          s = utils.Shell()
          s.__enter__()
          self.assertRaises(ConfigError, s.__exit__, 'type', 'value', 'tracebook')
  
subject: Test isexecutable check in utils.Shell