What is the preferred way to test event producers (Scenario vs AsseriblePublishedEvents)?

[nikimicallef]

The documentation shows two ways to test Transactional Event Producers. One uses Scenario.simulate(...) and the other requires you to invoke the method to directly, then use AssertiblePublishedEvents.ofType(...) to verify published events.

Below are two examples of these two approaches:

@Test
void createAsset_validAssetParameters_assetCreatedSuccessfully_usingScenario(Scenario scenario) {

    final String id = RandomStringUtils.randomAlphanumeric(8);
    final AssetEntity savedEntity = new AssetEntity(id);

    when(assetRepository.save(any(AssetEntity.class))).thenReturn(savedEntity);

    scenario.stimulate(() -> assetService.createAsset(assetType, assetTitle))
        .andWaitForEventOfType(AssetCreatedEvent.class)
        .matchingMappedValue(AssetCreatedEvent::getAssetId, id)
        .toArriveAndAssert((eventProduced,returnValue) -> assertReturnedDto(id));

    verify(assetRepository).save(any(AssetEntity.class));
}

@Test
void createAsset_validAssetParameters_assetCreatedSuccessfully(AssertablePublishedEvents publishedEvents) {

    final String id = RandomStringUtils.randomAlphanumeric(8);
    final AssetEntity savedEntity = new AssetEntity(id);

    when(assetRepository.save(any(AssetEntity.class))).thenReturn(savedEntity);

    final AssetDTO assetDTO = assetService.createAsset(assetType, assetTitle);

    assertNotNull(assetDTO);
    assertEquals(id, assetDTO.getId().id());

    verify(assetRepository).save(any(AssetEntity.class));

    assertTrue(publishedEvents.eventOfTypeWasPublished(AssetCreatedEvent.class));

    final PublishedEvents.TypedPublishedEvents<AssetCreatedEvent> matching = publishedEvents.ofType(AssetCreatedEvent.class)
        .matching(AssetCreatedEvent::getId, assetDTO.getId());
}

From my understanding, these two do the same thing, but I do not know which is the preferred/better approach. Does it matter at all? Happy to get feedback.

[odrotbohm]

We generally recommend Scenario as it provides a simplified, more guided API on how to set up a test scenario. It also deals with challenges stemming from the potentially asynchronous integration by using Awaitility under the hood. This is especially helpful in case you test cascading, asynchronously handled events.

AssertablePublishedEvents on the other hand, requires a bit more ceremony, predates Scenario and is used by that under the covers. Using APE might feel more natural to folks familiar with general AssertJ assertions.

[nikimicallef]

Great, thank you.