@Test void delegatesIsOverCapacity() {
    Exception wayOver = new RejectedExecutionException();
    when(delegate.isOverCapacity(wayOver)).thenReturn(true);

    assertThat(forwarder.isOverCapacity(wayOver)).isEqualTo(true);

    verify(delegate).isOverCapacity(wayOver);
  }
This test is intentionally brittle. It should break if we add new methods on {@link
StorageComponent}!
zipkin/src/test/java/zipkin2/storage/ForwardingStorageComponentTest.java