diff --git a/spring-core/src/test/java/org/springframework/core/io/buffer/AbstractDataBufferAllocatingTests.java b/spring-core/src/test/java/org/springframework/core/io/buffer/AbstractDataBufferAllocatingTests.java
index 036c6f7c36..dc8717e0df 100644
--- a/spring-core/src/test/java/org/springframework/core/io/buffer/AbstractDataBufferAllocatingTests.java
+++ b/spring-core/src/test/java/org/springframework/core/io/buffer/AbstractDataBufferAllocatingTests.java
@@ -46,7 +46,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
 
 /**
- * Base class for tests that read or write data buffers with a rule to check
+ * Base class for tests that read or write data buffers with an extension to check
  * that allocated buffers have been released.
  *
  * @author Arjen Poutsma
@@ -56,7 +56,7 @@ import static org.junit.jupiter.params.provider.Arguments.arguments;
 public abstract class AbstractDataBufferAllocatingTests {
 
 	@RegisterExtension
-	AfterEachCallback leakDetector = context -> verifyAllocations();
+	AfterEachCallback leakDetector = context -> waitForDataBufferRelease(Duration.ofSeconds(2));
 
 	protected DataBufferFactory bufferFactory;
 
@@ -94,7 +94,7 @@ public abstract class AbstractDataBufferAllocatingTests {
 	/**
 	 * Wait until allocations are at 0, or the given duration elapses.
 	 */
-	protected void waitForDataBufferRelease(Duration duration) throws InterruptedException {
+	private void waitForDataBufferRelease(Duration duration) throws InterruptedException {
 		Instant start = Instant.now();
 		while (true) {
 			try {
diff --git a/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageWriterTests.java b/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageWriterTests.java
index 1fd2a75336..68cf59d39c 100644
--- a/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageWriterTests.java
+++ b/spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageWriterTests.java
@@ -49,7 +49,7 @@ import static org.springframework.core.ResolvableType.forClass;
  * @author Sam Brannen
  */
 @SuppressWarnings("rawtypes")
-public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAllocatingTests {
+class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAllocatingTests {
 
 	private static final Map<String, Object> HINTS = Collections.emptyMap();
 
@@ -58,7 +58,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 
 
 	@ParameterizedDataBufferAllocatingTest
-	public void canWrite(String displayName, DataBufferFactory bufferFactory) {
+	void canWrite(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		assertThat(this.messageWriter.canWrite(forClass(Object.class), null)).isTrue();
@@ -73,7 +73,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void writeServerSentEvent(String displayName, DataBufferFactory bufferFactory) {
+	void writeServerSentEvent(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		ServerSentEvent<?> event = ServerSentEvent.builder().data("bar").id("c42").event("foo")
@@ -91,7 +91,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void writeString(String displayName, DataBufferFactory bufferFactory) {
+	void writeString(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		MockServerHttpResponse outputMessage = new MockServerHttpResponse(super.bufferFactory);
@@ -106,7 +106,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void writeMultiLineString(String displayName, DataBufferFactory bufferFactory) {
+	void writeMultiLineString(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		MockServerHttpResponse outputMessage = new MockServerHttpResponse(super.bufferFactory);
@@ -121,7 +121,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest // SPR-16516
-	public void writeStringWithCustomCharset(String displayName, DataBufferFactory bufferFactory) {
+	void writeStringWithCustomCharset(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		MockServerHttpResponse outputMessage = new MockServerHttpResponse(super.bufferFactory);
@@ -142,7 +142,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest
-	public void writePojo(String displayName, DataBufferFactory bufferFactory) {
+	void writePojo(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		MockServerHttpResponse outputMessage = new MockServerHttpResponse(super.bufferFactory);
@@ -157,7 +157,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest  // SPR-14899
-	public void writePojoWithPrettyPrint(String displayName, DataBufferFactory bufferFactory) {
+	void writePojoWithPrettyPrint(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		ObjectMapper mapper = Jackson2ObjectMapperBuilder.json().indentOutput(true).build();
@@ -179,7 +179,7 @@ public class ServerSentEventHttpMessageWriterTests extends AbstractDataBufferAll
 	}
 
 	@ParameterizedDataBufferAllocatingTest // SPR-16516, SPR-16539
-	public void writePojoWithCustomEncoding(String displayName, DataBufferFactory bufferFactory) {
+	void writePojoWithCustomEncoding(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;
 
 		MockServerHttpResponse outputMessage = new MockServerHttpResponse(super.bufferFactory);
diff --git a/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java b/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java
index 6624c5cd87..758d8f625a 100644
--- a/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java
+++ b/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java
@@ -26,7 +26,6 @@ import io.netty.channel.ChannelOption;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import org.junit.jupiter.api.AfterAll;
-import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.TestInstance;
 import reactor.core.publisher.Mono;
@@ -95,11 +94,6 @@ class WebClientDataBufferAllocatingTests extends AbstractDataBufferAllocatingTes
 		}
 	}
 
-	@AfterEach
-	void shutDown() throws InterruptedException {
-		waitForDataBufferRelease(Duration.ofSeconds(2));
-	}
-
 
 	@ParameterizedDataBufferAllocatingTest
 	void bodyToMonoVoid(String displayName, DataBufferFactory bufferFactory) {