code: @Test public void should_fail_if_actual_contains_given_values_more_than_once(){
    AssertionInfo info=someInfo();
    actual=array("Luke","Yoda","Han","Luke","Yoda","Han","Yoda","Luke");
    String[] expected={"Luke","Yoda","Leia"};
    try {
      arrays.assertContainsOnlyOnce(info,actual,expected);
    }
   catch (  AssertionError e) {
      verify(failures).failure(info,shouldContainsOnlyOnce(actual,expected,newLinkedHashSet("Leia"),newLinkedHashSet("Luke","Yoda")));
      return;
    }
    failBecauseExpectedAssertionErrorWasNotThrown();
  }
  