[question] how to mock reactive stack

[bilak]

Please provide the following information:

• Version of JMockit that was used: 1.49

• Description of the problem or enhancement request: I'm trying to mock the results of some repository methods. These methods are returning reactive (Mono/Flux) objects. When I mock more methods in one class all returns the first mock result. I don't understand what is the problem here.

The test sample is here

• Check the following:

  • [x] If a defect or unexpected result, JMockit project members should be able to reproduce it. For that, include an example test (perhaps accompanied by a Maven/Gradle build script) which can be executed without changes and reproduces the failure.

  • [ ] If an enhancement or new feature request, it should be justified by an example test demonstrating the validity and usefulness of the desired enhancement or new feature.

  • [x] The issue does not fall outside the scope of the project (for example, attempting to use JMockit APIs from Groovy or Scala code, or with an Android runtime).

  • [x] The JDK where the problem occurs is a final release, not a development build.

[Saljack]

It is a bug. I tested it with @Capturing DemoRepositoryImpl demoRepository and it works without any problem. So I tried to add times =1 into the Expectations.

new Expectations() {{
  demoRepository.testMethodOne();
  result = Mono.just("monoone");
  times = 1;

  demoRepository.testMethodTwo();
  result = Mono.just("monotwo");
  times = 1;
}};

and changed an implementation in the method callMonoMethods to:

@Override
public String callMonoMethods() {
  Mono<String> one = demoRepository.testMethodOne();
  Mono<String> two = demoRepository.testMethodTwo();
  return Mono.zip(one, two)
    .map(tuple -> tuple.getT1() + tuple.getT2())
    .block();
}

and then an exception is thrown:

Unexpected invocation to:
com.example.demo.data.repository.CustomDemoRepository#testMethodOne()

but it is from a call of testMethodTwo

[rliesenfeld]

Can't reproduce the failure without the code under test.

[bilak]

Can't reproduce the failure without the code under test.

@rliesenfeld What you mean by that? Did you run the tests and they are working properly?

[rliesenfeld]

Ah ok, now I see all the code is under https://github.com/bilak-poc/jmockit-reactive.

[rliesenfeld]

I get org.junit.jupiter.api.extension.ParameterResolutionException: No ParameterResolver registered for parameter [com.example.demo.data.repository.DemoRepository demoRepository] in method [void com.example.demo.DemoApplicationTests.testMono(com.example.demo.data.repository.DemoRepository)].

Which, of course, occurs because JMockit isn't getting initialized, due to missing configuration in the pom.xml.

[bilak]

let me fix the example, maybe I just copied something wrong from our application

[rliesenfeld]

With a simplified version of the code which still uses the Reactive API (Mono), it works fine for me:

final class DemoApplicationTests {
    @Tested TestService testService;
    @Injectable DemoRepository demoRepository;

    @Test
    void testMono() {
        new Expectations() {{
            demoRepository.getOne(); result = Mono.just("monoone");
            demoRepository.getTwo(); result = Mono.just("monotwo");
        }};

        var result = testService.callMonoMethods();

        assertEquals("monoonemonotwo", result);
    }
}

@Service
public final class TestService {
    @Autowired private DemoRepository demoRepository;

    public String callMonoMethods() {
        return Mono.zip(demoRepository.getOne(), demoRepository.getTwo())
            .map(tuple -> tuple.getT1() + tuple.getT2())
            .block();
    }
}

public interface DemoRepository {
    Mono<String> getOne();
    Mono<String> getTwo();
}

[bilak]

@rliesenfeld I've fixed the config. Why then it's not working with my configuration? We are using mainly integration tests where we are trying to use @Capturing parameter only for some objects through method parameter. If we use @Capturing as a test class field then we have other problems.

[Saljack]

I think the problem is with combination of Spring Data and JMockit. Spring Data generates Method implementation by JDK proxy.

[rliesenfeld]

Yes, it seems related to bytecode generated by the Spring framework. And @Capturing does not apply to dynamically generated classes.

In this case, the goal was to mock Repository interfaces in integration tests. I suggest to not mock them and just create actual integration tests.