How to test Spring @EventListener method?

Question

I have some event publishing:

@Autowired private final ApplicationEventPublisher publisher;
...
publisher.publishEvent(new MyApplicationEvent(mySource));
         


        

Answer 1

In case, spinning up the whole Spring context is not an option, with Spring Boot 2.0.0 ApplicationContextRunner was introduced.

ApplicationContextRunner can create an application context in your test, allowing for more control over the context.

A complete test example could be:

package net.andreaskluth.context.sample;

import static org.assertj.core.api.Assertions.assertThat;

import java.util.concurrent.atomic.AtomicBoolean;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.runner.ApplicationContextRunner;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

public class SimpleEventTest {

  private final ApplicationContextRunner runner = new ApplicationContextRunner();

  @Test
  public void happyPathSuccess() {
    AtomicBoolean sideEffectCausedByEvent = new AtomicBoolean(false);
    ObservableEffect effect = () -> sideEffectCausedByEvent.set(true);

    runner
        .withBean(SomeEventListener.class, effect)
        .run(
            context -> {
              context.publishEvent(new SomeEvent());
              assertThat(sideEffectCausedByEvent.get()).isTrue();
            });
  }

  public interface ObservableEffect {
    void effect();
  }

  @Component
  public static class SomeEventListener {

    private final ObservableEffect effect;

    public SomeEventListener(ObservableEffect effect) {
      this.effect = effect;
    }

    @EventListener(SomeEvent.class)
    public void listen() {
      effect.effect();
    }
  }

  public static class SomeEvent {}
}