public Mono<Integer> getInvocationCount() {
        return Mono.just(this.count.get());
    }
@Test
    public void givenSleepBy100ms_whenGetInvocationCount_thenIsGreaterThanZero()
            throws InterruptedException {
        Thread.sleep(100L);
        counter.getInvocationCount()
                .as(StepVerifier::create)
                .consumeNextWith(count -> assertThat(count).isGreaterThan(0))
                .thenCancel()
                .verify();
    }