Unit testing retry in Spring Webflux with mocked response

Question

During unit testing retry the response of the mock seems cached, or most probably I am doing something wrong.

I am trying to request something, if error happened then retry twice with delay of 1 second.

  public Mono<Object> someMethod(String someParam) {
    return someInjectedService.doSomething(someParam)
        .doOnError(ex -> System.out.println(ex + ": " + System.currentTimeMillis()))
        .retryWhen(Retry.fixedDelay(2, Duration.ofSeconds(1)).filter(ex -> ex instanceof SomeCustomException))
        .doOnSuccess(result -> doSomethingOnSuccess(result));
  }

My test:

  @Test
  void testshouldRequestThrice_whenErrorOccurs() {
    // Given
    String someParam = "testParam";
    when(someInjectedService.doSomething(someParam))
        .thenReturn(Mono.error(new SomeCustomException("SomeCustomException"))) // 1st response
        .thenReturn(Mono.error(new SomeCustomException("SomeCustomException"))) // 2nd response
        .thenReturn(Mono.just("SomeValidResponse")); // 3rd valid response

    // When
    var result = testService.someMethod(someParam).block();

    // Then
    // Initial request, followed by two retries
    verify(someInjectedService, times(3)).doSomething(someParam);
  }

here someInjectedService is a mock. My plan was to return an exception twice, and on third request return valid response. But what I get is:

org.mockito.exceptions.verification.TooFewActualInvocations: someInjectedService.doSomething("testParam");

Wanted 3 times: -> at shouldRequestThrice_whenErrorOccurs(test.java:138)

But was 1 time:

While I do see 3 prints from .doOnError(ex -> System.out.println(ex + ": " + System.currentTimeMillis())) block, I feel like the actual request is sent only once.

Thank you in advance,

Dangelo

If I'm not wrong, someInjectedService.doSomething(...) will indeed technically be called only once, it's the returned mono that will be retried. – Focus

@Focus hi, any idea on how I can approach this? – Dangelo

You could Mono.defer(() -> someInjectedService.doSomething(someParam)) to ensure the method is effectively called again, which should make your test pass. – Focus

@Focus thank you, solution is so easy, do you mind posting it as an answer? – Dangelo

I faced the same problem, could you please explain, in the example above, where this line should be added? Mono.defer(() -> someInjectedService.doSomething(someParam)) – Opinicus

@Opinicus Hi, it should be added right after return, replace this line return someInjectedService.doSomething(someParam) with return Mono.defer(() -> someInjectedService... Bla bla) – Dangelo

Answer 1

someInjectedService.doSomething(...) will indeed technically be called only once.

You could use Mono.defer(() -> someInjectedService.doSomething(someParam)) instead, to ensure the method is effectively called again, which should make your test pass.

Focus