@Test
 public void should_fail_if_actual_does_not_contain_values() {
   actual = list("Han", "Luke");
   try {
     lists.assertContainsNull(description, actual);
   } catch (AssertionError e) {
     verify(failures).failure(description, shouldContainNull(actual));
     return;
   }
   expectedAssertionErrorNotThrown();
 }
 @Test
 public void should_pass_if_actual_contains_given_values_more_than_once() {
   actual.addAll(list(null, "Luke", null));
   lists.assertContainsNull(description, actual);
 }
 @Test
 public void should_fail_if_actual_is_null() {
   thrown.expect(AssertionError.class, FailureMessages.actualIsNull());
   lists.assertContainsNull(description, null);
 }
 @Test
 public void should_pass_if_actual_contains_null() {
   TestDescription description = new TestDescription("description for test");
   lists.assertContainsNull(description, actual);
 }