Mocks and Guice

[Andres Almiray]

Hello everyone,

I'm exploring Spock's options for binding mocks with Guice given spock-guice. I've encountered a few problems and would like to get your advice on the matter.

The CUT looks like this

public class AppController {
    @Inject private AppModel model;
    @Inject private Github github;
    @Inject private ApplicationEventBus eventBus;

    public void loadRepositories() {
        model.setState(RUNNING);
        github.repositories(model.getOrganization())
            .done(model.getRepositories()::addAll)
            .fail(throwable -> eventBus.publishAsync(new ThrowableEvent(throwable)))
            .always((state, resolved, rejected) -> model.setState(READY));
    }
}

The `Github` type is the one I'm interested in mocking out. My first attempt to mock this type and define an interaction for it is shown next

@UseModules(TestModule)
class AppControllerSpec extends Specification {
    private static final String ORGANIZATION = 'foo'

    @Inject private AppController controller
    @Inject private AppModel model
    @Inject private ApplicationEventBus eventBus
    @Inject private Github github

    def happyPath() {
        given:
        Collection<Repository> repositories = TestHelper.createSampleRepositories()
        Promise<Collection<Repository>, Throwable, Void> promise = new DeferredObject<Collection<Repository>, Throwable, Void>().resolve(repositories)
        github.repositories(ORGANIZATION) >> promise

        when:
        model.organization = ORGANIZATION
        controller.loadRepositories()

        then:
        model.repositories.size() == 3
        model.repositories == repositories

        1 * github.repositories(ORGANIZATION)
    }

    static class TestModule extends AppModule {
        private final MockFactory mockFactory = new DetachedMockFactory()

        @Override
        protected void bindGithub() {
            bind(Github).toInstance(mockFactory.Mock(Github))
        }
    }
}

Unfortunately the `AppController` class complains with an NPE as `grihub.repositories('foo')` returns  a `null` as a default empty response. This means the interaction was ignored. Next I tried an explicit Mock in place but that caused the same NPE

@UseModules(AppModule)
class AppControllerSpec extends Specification {
    private static final String ORGANIZATION = 'foo'

    @Inject private AppController controller
    @Inject private AppModel model
    @Inject private ApplicationEventBus eventBus

    def happyPath() {
        given:
        Collection<Repository> repositories = TestHelper.createSampleRepositories()
        Promise<Collection<Repository>, Throwable, Void> promise = new DeferredObject<Collection<Repository>, Throwable, Void>().resolve(repositories)
        controller.@github  = Mock(Github) {
            repositories(ORGANIZATION) >> promise
        }

        when:
        model.organization = ORGANIZATION
        controller.loadRepositories()

        then:
        model.repositories.size() == 3
        model.repositories == repositories

        1 * github.repositories(ORGANIZATION)
    }
}

Next I turned to making the Mock a simple Stub and got the same problem. Just for kicks started to play around with wildcards and ended up with a working version

@UseModules(AppModule)
class AppControllerSpec extends Specification {
    private static final String ORGANIZATION = 'foo'

    @Inject private AppController controller
    @Inject private AppModel model
    @Inject private ApplicationEventBus eventBus

    def happyPath() {
        given:
        Collection<Repository> repositories = TestHelper.createSampleRepositories()
        Promise<Collection<Repository>, Throwable, Void> promise = new DeferredObject<Collection<Repository>, Throwable, Void>().resolve(repositories)
        controller.@github = Stub(Github) {
            _(ORGANIZATION) >> promise
        }

        when:
        model.organization = ORGANIZATION
        controller.loadRepositories()

        then:
        model.repositories.size() == 3
        model.repositories == repositories
    }
}

While it works it kind of defeats the purpose of using a DI container and mocks together, besides the use of a wildcard in this particular case is less than optimal. Any hints to make the code simpler, perhaps making it look like the first snippet, would be appreciated.

Spock 1.1-groovy-2.4
Groovy 2.4.12
Guice 4.1.0

Source code available at https://github.com/aalmiray/javatrove/tree/master/github-api-01.

Thanks!

[Andres Almiray]