GH-3873: Deprecate JUnit 4 utilities in the project

spring-kafka-docs/src/main/antora/modules/ROOT/pages/testing.adoc

@@ -56,8 +56,7 @@ If this is not possible for some reason, note that the `consumeFromEmbeddedTopic
 Since it does not have access to the consumer properties, you must use the overloaded method that takes a `seekToEnd` boolean parameter to seek to the end instead of the beginning.
 ====
 
-NOTE: The `EmbeddedKafkaRule` JUnit 4 rule has been removed in version 4.0.
-For JUnit 4, you should use the `EmbeddedKafkaKraftBroker` directly or migrate to JUnit 5 with the `@EmbeddedKafka` annotation.
+NOTE: `Spring Kafka` no longer supports JUnit4. Please consider migrating from JUnit4 to JUnit5.
 
 The `EmbeddedKafkaBroker` class has a utility method that lets you consume for all the topics it created.
 The following example shows how to use it:
@@ -121,15 +120,19 @@ The following example configuration creates topics called `cat` and `hat` with f
 
 [source, java]
 ----
+@SpringJUnitConfig
+@EmbeddedKafka(
+		partitions = 5,
+		topics = {"cat", "hat"}
+)
 public class MyTests {
 
-    @ClassRule
-    private static EmbeddedKafkaRule embeddedKafka = new EmbeddedKafkaRule(1, false, 5, "cat", "hat");
+    @Autowired
+    private EmbeddedKafkaBroker broker;
 
     @Test
     public void test() {
-        embeddedKafkaRule.getEmbeddedKafka()
-              .addTopics(new NewTopic("thing1", 10, (short) 1), new NewTopic("thing2", 15, (short) 1));
+        broker.addTopics(new NewTopic("thing1", 10, (short) 1), new NewTopic("thing2", 15, (short) 1));
         ...
     }
 
@@ -225,7 +228,7 @@ The following example shows how to use it:
 
 [source, java]
 ----
-@RunWith(SpringRunner.class)
+@SpringJUnitConfig
 @DirtiesContext
 @EmbeddedKafka(partitions = 1,
          topics = {
@@ -237,7 +240,7 @@ public class KafkaStreamsTests {
     private EmbeddedKafkaBroker embeddedKafka;
 
     @Test
-    public void someTest() {
+    void someTest() {
         Map<String, Object> consumerProps = KafkaTestUtils.consumerProps("testGroup", "true", this.embeddedKafka);
         consumerProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
         ConsumerFactory<Integer, String> cf = new DefaultKafkaConsumerFactory<>(consumerProps);
@@ -288,7 +291,7 @@ In addition, the broker properties are loaded from the `broker.properties` class
 Property placeholders are resolved for the `brokerPropertiesLocation` URL and for any property placeholders found in the resource.
 Properties defined by `brokerProperties` override properties found in `brokerPropertiesLocation`.
 
-You can use the `@EmbeddedKafka` annotation with JUnit 4 or JUnit 5.
+You can use the `@EmbeddedKafka` annotation with JUnit 5.
 
 [[embedded-kafka-junit5]]
 == `@EmbeddedKafka` Annotation with JUnit5
@@ -333,7 +336,7 @@ The following example shows how to do so:
 =====
 [source, java]
 ----
-@RunWith(SpringRunner.class)
+@SpringJUnitConfig
 @SpringBootTest(properties = "spring.autoconfigure.exclude="
     + "org.springframework.cloud.stream.test.binder.TestSupportBinderAutoConfiguration")
 public class MyApplicationTests {
@@ -347,37 +350,8 @@ There are several ways to use an embedded broker in a Spring Boot application te
 
 They include:
 
-* xref:testing.adoc#kafka-testing-junit4-class-rule[JUnit4 Class Rule]
 * xref:testing.adoc#kafka-testing-embeddedkafka-annotation[`@EmbeddedKafka` Annotation or `EmbeddedKafkaBroker` Bean]
 
-[[kafka-testing-junit4-class-rule]]
-=== JUnit4 Class Rule
-
-The following example shows how to use a JUnit4 class rule to create an embedded broker:
-
-[source, java]
-----
-@RunWith(SpringRunner.class)
-@SpringBootTest
-public class MyApplicationTests {
-
-    @ClassRule
-    public static EmbeddedKafkaRule broker = new EmbeddedKafkaRule(1, false, "someTopic")
-            .brokerListProperty("spring.kafka.bootstrap-servers");
-
-    @Autowired
-    private KafkaTemplate<String, String> template;
-
-    @Test
-    public void test() {
-        ...
-    }
-
-}
-----
-
-Notice that, since this is a Spring Boot application, we override the broker list property to set Spring Boot's property.
-
 [[embedded-broker-with-springjunitconfig-annotations]]
 == `@EmbeddedKafka` with `@SpringJunitConfig`
 
@@ -395,7 +369,7 @@ The following example shows how to use an `@EmbeddedKafka` Annotation to create
 
 [source, java]
 ----
-@RunWith(SpringRunner.class)
+@SpringJUnitConfig
 @EmbeddedKafka(topics = "someTopic",
         bootstrapServersProperty = "spring.kafka.bootstrap-servers") // this is now the default
 public class MyApplicationTests {
@@ -404,7 +378,7 @@ public class MyApplicationTests {
     private KafkaTemplate<String, String> template;
 
     @Test
-    public void test() {
+    void test() {
         ...
     }
 

spring-kafka-test/src/main/java/org/springframework/kafka/test/context/EmbeddedKafka.java

@@ -43,7 +43,7 @@
  * <p>
  * The typical usage of this annotation is like:
  * <pre class="code">
- * &#064;RunWith(SpringRunner.class)
+ * &#064;SpringJUnitConfig
  * &#064;EmbeddedKafka
  * public class MyKafkaTests {
  *
@@ -67,6 +67,7 @@
  * @author Pawel Lozinski
  * @author Adrian Chlebosz
  * @author Soby Chacko
+ * @author Sanghyeok An
  *
  * @since 1.3
  *
@@ -169,4 +170,3 @@
 	int adminTimeout() default EmbeddedKafkaBroker.DEFAULT_ADMIN_TIMEOUT;
 
 }
-

spring-kafka-test/src/main/java/org/springframework/kafka/test/rule/Log4j2LevelAdjuster.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -37,8 +37,11 @@
  * @author Dave Syer
  * @author Artem Bilan
  * @author Gary Russell
+ * @author Sanghyeok An
  *
+ * @deprecated since 4.0 in favor of {@link org.springframework.kafka.test.condition.LogLevels}.
  */
+@Deprecated(since = "4.0", forRemoval = true)
 public class Log4j2LevelAdjuster implements MethodRule {
 
 	private final List<Class<?>> classes;

spring-kafka-test/src/test/java/org/springframework/kafka/test/rule/AddressableEmbeddedBrokerTests.java → spring-kafka-test/src/test/java/org/springframework/kafka/test/AddressableEmbeddedBrokerTests.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.kafka.test.rule;
+package org.springframework.kafka.test;
 
 import java.io.IOException;
 import java.net.ServerSocket;
@@ -32,7 +32,6 @@
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.kafka.test.EmbeddedKafkaKraftBroker;
 import org.springframework.kafka.test.utils.KafkaTestUtils;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;