Adjust checkForLeaks timeout settings

LeakAwareDataBufferFactory#checkForLeaks automatically waits up to 5
sec for buffers to be released, which could be used as a way of
awaiting on some async logic to complete, and as long as buffers are
released, it shouldn't be long. However, the leak test in
LeakAwareDataBufferFactoryTests actually expects to find a leak, and
always ends up waiting the full 5 seconds.

This change, makes the wait configurable, with the no-arg method
using 0 (no waiting). AbstractLeakCheckingTests uses 1 second by
default since ResourceRegionEncoderTests did fail locally. If more
tests need this, we can adjust the settings.

spring-core/src/test/java/org/springframework/core/codec/ResourceRegionEncoderTests.java

@@ -63,7 +63,7 @@ class ResourceRegionEncoderTests extends AbstractLeakCheckingTests {
 	}
 
 	@Test
-	void shouldEncodeResourceRegionFileResource() throws Exception {
+	void shouldEncodeResourceRegionFileResource() {
 		ResourceRegion region = new ResourceRegion(
 				new ClassPathResource("ResourceRegionEncoderTests.txt", getClass()), 0, 6);
 		Flux<DataBuffer> result = this.encoder.encode(Mono.just(region), this.bufferFactory,

spring-core/src/test/java/org/springframework/core/io/buffer/LeakAwareDataBufferFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,8 +35,7 @@ class LeakAwareDataBufferFactoryTests {
 	void leak() {
 		DataBuffer dataBuffer = this.bufferFactory.allocateBuffer();
 		try {
-			assertThatExceptionOfType(AssertionError.class).isThrownBy(
+			assertThatExceptionOfType(AssertionError.class).isThrownBy(this.bufferFactory::checkForLeaks);
-					this.bufferFactory::checkForLeaks);
 		}
 		finally {
 			release(dataBuffer);

spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/AbstractLeakCheckingTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.core.testfixture.io.buffer;
 
+import java.time.Duration;
+
 import org.junit.jupiter.api.AfterEach;
 
 import org.springframework.core.io.buffer.DataBufferFactory;
@@ -42,7 +44,7 @@ public abstract class AbstractLeakCheckingTests {
 	 */
 	@AfterEach
 	final void checkForLeaks() {
-		this.bufferFactory.checkForLeaks();
+		this.bufferFactory.checkForLeaks(Duration.ofSeconds(1));
 	}
 
 }

spring-core/src/testFixtures/java/org/springframework/core/testfixture/io/buffer/LeakAwareDataBufferFactory.java

@@ -81,13 +81,21 @@ public class LeakAwareDataBufferFactory implements DataBufferFactory {
 	 * method.
 	 */
 	public void checkForLeaks() {
+		checkForLeaks(Duration.ofSeconds(0));
+	}
+
+	/**
+	 * Variant of {@link #checkForLeaks()} with the option to wait for buffer release.
+	 * @param timeout how long to wait for buffers to be released; 0 for no waiting
+	 */
+	public void checkForLeaks(Duration timeout) {
 		this.trackCreated.set(false);
 		Instant start = Instant.now();
 		while (true) {
 			if (this.created.stream().noneMatch(LeakAwareDataBuffer::isAllocated)) {
 				return;
 			}
-			if (Instant.now().isBefore(start.plus(Duration.ofSeconds(5)))) {
+			if (Instant.now().isBefore(start.plus(timeout))) {
 				try {
 					Thread.sleep(50);
 				}