How to verify with StepVerifier that provided Mono did not completed?

问题

With StepVerifier it is very easy to check whether provided Mono has completed (just by expectComplete() method in StepVerifier), but what should I do if need to check the opposite case ?

I tried to use this approach:

    @Test
    public void neverMonoTest() {
        Mono<String> neverMono = Mono.never();
        StepVerifier.create(neverMono)
            .expectSubscription()
            .expectNoEvent(Duration.ofSeconds(1))
            .thenCancel()
            .verify();
    }

and such test passes. But this is false positive, because when I replace Mono.never() with Mono.empty() the test is still green.

Is there any better and reliable method to check lack of Mono's completion (of course within given scope of time) ?

回答1:

It looks like you're hitting a bug in reactor-test, and unfortunately one that doesn't look to be solved any time soon:

Due to my memory that was a constant flaw in design of reactor-test. Most likely that will be fixed once reactor-test will be rewritten from scratch / significantly.

Downgrading to 3.1.2 seems to fix the problem, but that's quite a downgrade. The only other workaround I'm aware of was posted by PyvesB here, and involves waiting for the Mono to timeout:

Mono<String> mono = Mono.never();
StepVerifier.create(mono.timeout(Duration.ofSeconds(1L)))
        .verifyError(TimeoutException.class);

When the next release rolls out, then you should be able to do:

Mono<String> mono = Mono.never();
StepVerifier.create(mono)
        .expectTimeout(Duration.ofSeconds(1));

...as a more concise alternative.

来源：https://stackoverflow.com/questions/58486417/how-to-verify-with-stepverifier-that-provided-mono-did-not-completed

标签

project-reactor