Introduce ApplicationEvents abstraction to capture application events published during a test

[odrotbohm]

PublishedEventsExtension registers a composite ApplicationListener backed by thread-bound individual listeners to capture all application events published during the execution of a test method. Those would declare a PublishedEvents parameter to the method which provides API to define assertions based on the events published:

@ExtendWith(PublishedEventsExtension.class) class SampleTests { @Test void someTestMethod(PublishedEvents events) { // Filter events by type and predicate assertThat(events.ofType(MyEventType.class).matching(it -> …)).hasSize(2); } }

[sbrannen]

Thanks for the PR!

Tentatively slated for 5.3 RC1 for review and potential inclusion in 5.3

[sbrannen]

The current proposal introduces support for the following abstraction.

/**  * {@code ApplicationEvents} encapsulates all {@linkplain ApplicationEvent  * application events} that were fired during the execution of a single test  * method.  *  * @author Sam Brannen  * @author Oliver Drotbohm  * @since 5.3.1  * @see ApplicationEventsExtension  * @see org.springframework.context.ApplicationEvent  * @see org.springframework.context.ApplicationListener  */ public interface ApplicationEvents { /**  * Stream all application events that were fired during test execution.  * @return a stream of all application events  */ Stream<ApplicationEvent> stream(); /**  * Stream all application events or event payloads of the given type that  * were fired during test execution.  * @param <T> the event type  * @param type the type of events or payloads to stream; never {@code null}  * @return a stream of all application events or event payloads of the  * specified type  */	<T> Stream<T> stream(Class<T> type); }

Current work on this issue can be viewed in the following branch that builds on top of this PR: master...sbrannen:issues/gh-25616-application-events-extension

Tentatively slated for inclusion in 5.3.2.

[odrotbohm]

Lovely! Thanks for all the extra effort you put into this, @sbrannen! 🙇

[sbrannen]

You're very welcome!

Thanks for the idea, the prototype, and for your patience. :)