GH-1131 - Non-empty collections do not indicate scenario completion anymore.

Similarly to our treatment of Optional, we now only consider non-empty collections a trigger for a state change based Scenario conclusion.

spring-modulith-test/src/test/java/org/springframework/modulith/test/ScenarioUnitTests.java

@@ -23,7 +23,9 @@ import lombok.RequiredArgsConstructor;
 
 import java.lang.Thread.UncaughtExceptionHandler;
 import java.time.Duration;
+import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -433,6 +435,57 @@ class ScenarioUnitTests {
 		verify(runnable).run();
 	}
 
+	@Test // GH-1131
+	void concludesForNonEmptyOptional() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitForStateChange(delayed(Optional.of("value"))))
+						.expectSuccess();
+	}
+
+	@Test // GH-1131
+	void doesNotConcludeForEmptyOptional() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitAtMost(Duration.ofMillis(500))
+				.andWaitForStateChange(delayed(Optional.empty())))
+						.expectFailure();
+	}
+
+	@Test // GH-1131
+	void concludesForNonEmptyCollection() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitForStateChange(delayed(List.of("value"))))
+						.expectSuccess();
+	}
+
+	@Test // GH-1131
+	void doesNotConcludeForEmptyCollection() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitAtMost(Duration.ofMillis(500))
+				.andWaitForStateChange(delayed(Collections.emptyList())))
+						.expectFailure();
+	}
+
+	@Test // GH-1131
+	void concludesForNonNull() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitForStateChange(delayed(new Object())))
+						.expectSuccess();
+	}
+
+	@Test // GH-1131
+	void doesNotConcludeForNull() {
+
+		givenAScenario(it -> it.publish(new Object())
+				.andWaitAtMost(Duration.ofMillis(500))
+				.andWaitForStateChange(delayed(null)))
+						.expectFailure();
+	}
+
 	private Fixture givenAScenario(Consumer<Scenario> consumer) {
 		return new Fixture(consumer, DELAY, null, new DefaultAssertablePublishedEvents());
 	}