1565f4b83e
This commit introduces a new feature in the Spring TestContext
Framework (TCF) that provides support for recording application events
published in the ApplicationContext so that assertions can be performed
against those events within tests. All events published during the
execution of a single test are made available via the ApplicationEvents
API which allows one to process the events as a java.util.Stream.
The following example demonstrates usage of this new feature.
@SpringJUnitConfig(/* ... */)
@RecordApplicationEvents
class OrderServiceTests {
@Autowired
OrderService orderService;
@Autowired
ApplicationEvents events;
@Test
void submitOrder() {
// Invoke method in OrderService that publishes an event
orderService.submitOrder(new Order(/* ... */));
// Verify that an OrderSubmitted event was published
int numEvents = events.stream(OrderSubmitted.class).count();
assertThat(numEvents).isEqualTo(1);
}
}
To enable the feature, a test class must be annotated or meta-annotated
with @RecordApplicationEvents. Behind the scenes, a new
ApplicationEventsTestExecutionListener manages the registration of
ApplicationEvents for the current thread at various points within the
test execution lifecycle and makes the current instance of
ApplicationEvents available to tests via an @Autowired field in the
test class. The latter is made possible by a custom ObjectFactory that
is registered as a "resolvable dependency". Thanks to the magic of
ObjectFactoryDelegatingInvocationHandler in the spring-beans module,
the ApplicationEvents instance injected into test classes is
effectively a scoped-proxy that always accesses the ApplicationEvents
managed for the current test.
The current ApplicationEvents instance is stored in a ThreadLocal
variable which is made available in the ApplicationEventsHolder.
Although this class is public, it is only intended for use within the
TCF or in the implementation of third-party extensions.
ApplicationEventsApplicationListener is responsible for listening to
all application events and recording them in the current
ApplicationEvents instance. A single
ApplicationEventsApplicationListener is registered with the test's
ApplicationContext by the ApplicationEventsTestExecutionListener.
The SpringExtension has also been updated to support parameters of type
ApplicationEvents via the JUnit Jupiter ParameterResolver extension
API. This allows JUnit Jupiter based tests to receive access to the
current ApplicationEvents via test and lifecycle method parameters as
an alternative to @Autowired fields in the test class.
Closes gh-25616
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