Issues After Upgrading to JDK 21 and JUnit 5 in AEM Project – Need Guidance

Hi @murali__d,

Upgrading Java may be painless, but upgrading to JUnit 5 is not an easy task and requires many code changes. The most likely root causes in your case include:

• JUnit migration requirements: JUnit 5 has a completely different architecture than JUnit 4, with different annotations, assertions, and extension mechanisms. Your test code needs to be migrated to use the new JUnit 5 Jupiter API.​ How to migrate from JUnit 4 to JUnit 5: a step-by-step guide 
• Maven plugin compatibility: Older versions of Maven plugins (especially maven-surefire-plugin, bnd-maven-plugin, and aemanalyser-maven-plugin) may not support JDK 21, leading to build and test execution failures.​ Upgrading to Java 21 for AEM: What Developers Need to Know 
• Missing or incorrect test dependencies: The NoClassDefFoundError typically indicates missing runtime dependencies for test execution, particularly JUnit Platform dependencies. NoClassDefFoundError when trying to run JUnit 5 tests 

I warmly suggest that you take a look at these articles, which contain step-by-step instructions on how to do the upgrades.

Hello @murali__d ,

After the upgrade from JDK 11 + JUnit 4 to JDK 21 + JUnit 5, the test failures you are seeing (NullPointerException, NoClassDefFoundError, etc.) are expected. This happens because several dependencies, test frameworks, and plugins used earlier are not fully compatible with Java 21 or JUnit 5.

You do not need to fix each failing class manually. The root cause is the test setup itself, not the individual test logic.

>To resolve the issue, you will need to:

1. Update the Maven Surefire/Failsafe plugins to versions that support JUnit 5 and JDK 21.

2. Add the required JUnit 5 (jupiter) dependencies.

3. Upgrade Mockito/PowerMock/ByteBuddy libraries to versions compatible with Java 21.

4. Add back any libraries that were removed from the JDK (e.g., JAXB) if your tests use them.

Once the test framework and dependencies are updated, most of the failures will be resolved automatically. Only a few tests may require manual fixes afterward.

If you share your pom.xml or one full stacktrace, I can check further.