// Create a request that implements both CommonServerMessageBlockRequest and RequestWithFileId
        CommonServerMessageBlockRequest next =
                mock(CommonServerMessageBlockRequest.class, withSettings().extraInterfaces(RequestWithFileId.class));

        resp.prepare(next);

        verify((RequestWithFileId) next, times(1)).setFileId(eq(fileId));
    }

    @Test
    void prepare_doesNothing_whenNotReceived() {