@Test void delegatesCheck() {
    CheckResult down = CheckResult.failed(new RuntimeException("failed"));
    when(delegate.check()).thenReturn(down);

    assertThat(forwarder.check()).isEqualTo(down);

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