Polishing test

Assert that BlockHound doesn't trigger, rather than assertions on a
condition that makes the test flakky because concurrency is involved.

Author: simonbasle

spring-core/src/test/java/org/springframework/core/SpringCoreBlockHoundIntegrationTests.java

@@ -29,6 +29,7 @@
 import org.springframework.util.ConcurrentReferenceHashMap;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.jupiter.api.condition.JRE.JAVA_18;
 
@@ -107,8 +108,9 @@ void concurrentReferenceHashMapSegmentClear() {
 			}
 		}, future2);
 
-		CompletableFuture.allOf(future1, future2).join();
-		assertThat(map).isEmpty();
+		//ensure blockhound doesn't trigger
+		final CompletableFuture<Void> allOf = CompletableFuture.allOf(future1, future2);
+		assertThatNoException().isThrownBy(allOf::join);
 	}
 
 	private void testNonBlockingTask(NonBlockingTask task) {