    @Test
    public void dropElementsOnBackpressureTest() {

        DirectProcessor<String> processor = DirectProcessor.create();
        StepVerifier
                .create(dropElementsOnBackpressure(processor), 0)
                .expectSubscription()
                .then(() -> processor.onNext(""))
                .then(() -> processor.onNext(""))
                .thenRequest(1)
                .then(() -> processor.onNext("0"))
                .expectNext("0")
                .then(() -> processor.onNext("0"))
                .then(() -> processor.onNext("0"))
                .thenRequest(1)
                .then(() -> processor.onNext("10"))
                .expectNext("10")
                .thenRequest(1)
                .then(() -> processor.onNext("20"))
                .expectNext("20")
                .then(() -> processor.onNext("40"))
                .then(() -> processor.onNext("30"))
                .then(processor::onComplete)
                .expectComplete()
                .verify();
    }