@Override
  public void addArguments(Deque<String> args) {
    if (expression != null) {
      expression.addArguments(args);
    }
  }
@Test
  public void addArguments() {
    @SuppressWarnings("unchecked")
    Deque<String> args = mock(Deque.class);
    test.addArguments(args);
    verify(expr).addArguments(args);
    verifyNoMoreInteractions(expr);
  }