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,

If I'm not wrong, `someInjectedService.doSomething(...)` will indeed technically be called only once, it's the returned mono that will be retried. — sp00m, Jan 19 '22 at 12:08
You could `Mono.defer(() -> someInjectedService.doSomething(someParam))` to ensure the method is effectively called again, which should make your test pass. — sp00m, Jan 19 '22 at 12:16
@sp00m thank you, solution is so easy, do you mind posting it as an answer? — Hatik, Jan 19 '22 at 12:20
I faced the same problem, could you please explain, in the example above, where this line should be added? Mono.defer(() -> someInjectedService.doSomething(someParam)) — Denis, Jul 11 '22 at 08:42
@Denis Hi, it should be added right after `return`, replace this line `return someInjectedService.doSomething(someParam)` with `return Mono.defer(() -> someInjectedService... Bla bla)` — Hatik, Jul 11 '22 at 16:41

score 4 · Accepted Answer · answered Jan 19 '22 at 15:18

4

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.

answered Jan 19 '22 at 15:18

sp00m

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Unit testing retry in Spring Webflux with mocked response

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