public void addFilter(Filter filter) {
    filterChain.addFilter(filter);
  }
@Test
  void testAddFilter() {
    final var target = mock(Target.class);
    final var filterManager = new FilterManager();

    verifyNoMoreInteractions(target);

    final var filter = mock(Filter.class);
    when(filter.execute(any(Order.class))).thenReturn("filter");

    filterManager.addFilter(filter);

    final Order order = mock(Order.class);
    assertEquals("filter", filterManager.filterRequest(order));

    verify(filter, times(1)).execute(any(Order.class));
    verifyNoMoreInteractions(target, filter, order);
  }