Migrate log4j-slf4j2-impl to JUnit 5

[AlbaHerrerias]

Hello 👋

We are from Neighbourhoodie, the implementation partner of the STF Bug Resilience Program. This work is part of our agreed Milestone 1. Upgrade from JUnit 4 to JUnit 5. This PR migrates the tests located in log4j-slf4j2-impl.

⚠️ We've found out that OverflowTest is set to run specifically with Junit 4. This behaviour was added not long ago so we wanted to ask, should we leave it like this or should we refactor OverflowTest to JUnit 5?

Thank you!

Checklist

• Base your changes on 2.x branch if you are targeting Log4j 2; use main otherwise
• ./mvnw verify succeeds (if it fails due to code formatting issues reported by Spotless, simply run ./mvnw spotless:apply and retry)
• Non-trivial changes contain an entry file in the src/changelog/.2.x.x directory
• Tests for the changes are provided
• Commits are signed (optional, but highly recommended)

[github-actions]

Job	Requested goals	Build Tool Version	Build Outcome	Build Scan®
build-macos-latest	clean install	3.9.8	✅
build-ubuntu-latest	clean install	3.9.8	✅
build-windows-latest	clean install	3.9.8	✅

Generated by gradle/develocity-actions

[ppkarwasz]

This looks great, thanks!

Since the log4j-slf4j-impl module is mostly identical to this one (it has a couple of tests less). Could you apply the changes to that module too?

Could you also remove the junit-vintage-engine dependency in the pom.xml to show that not tests are using JUnit 4?

[ppkarwasz]

Suggested change

	assertTrue(ctx1 instanceof LifeCycle, "LoggerContext is not enabled for shutdown");
	assertInstanceOf(LifeCycle.class, ctx1, "LoggerContext is not enabled for shutdown");

Could you change the assertions on X instanceof Y to use the new assertInstanceOf assertions?

[ppkarwasz]

⚠️ We've found out that OverflowTest is set to run specifically with Junit 4. This behaviour was added not long ago so we wanted to ask, should we leave it like this or should we refactor OverflowTest to JUnit 5?

As far as I can tell OverflowTest does not depend specifically on JUnit 4. It only requires an additional dependency (log4j-to-slf4j). The module should detect that Log4j API is redirected to SLF4J and should not forward SLF4J calls back to Log4j API.
Taking advantage of new Maven Surefire Plugin capabilities I believe that such a configuration should work:

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <executions>
         <!-- Separate test execution to verify that the presence of both:
            ~  * `log4j-slf4j2-impl` (bridge from SLF4J to Log4j API)
            ~  * `log4j-to-slf4j` (bridge from Log4j API to SLF4J)
            ~  does not cause a stack overflow.
            -->
          <execution>
            <id>loop-test</id>
            <goals>
              <goal>test</goal>
            </goals>
            <configuration>
             <additionalClasspathDependencies>
               <dependency>
                 <groupId>org.apache.logging.log4j</groupId>
                 <artifactId>log4j-to-slf4j</artifactId>
                 <version>${project.version}</version>
               </dependency>
             </additionalClasspathDependencies>
              <includes>
                <include>**/OverflowTest.java</include>
              </includes>
            </configuration>
          </execution>
          <execution>
            <id>default-test</id>
            <configuration>
              <includes>
                <include>**/*Test.java</include>
              </includes>
              <excludes>
                <exclude>**/OverflowTest.java</exclude>
              </excludes>
            </configuration>
          </execution>
        </executions>
      </plugin>

and log4j-to-slf4j can be removed from the <dependencies> section of the project.

[AlbaHerrerias]

Thank you for the review and assistance, I have addressed now your requested changes. Please let me know if you'd like to request more.

I will make the refactor of the log4j-slf4j-impl module. My plan is to make it as a new PR (as we have been doing; a PR per module), but if you'd rather me doing it in this PR, please let me know and I will do so.

Also note that, with the removal of junit-vintage-engine, the tests of Log4j2_1482_Slf4jTest.java are not being executed (total of 2 tests). They
extend from log4j-core-test/.../Log4j2_1482_Test.java, currently written in JUnit 4. My coworker is refactoring those in #3061.

[ppkarwasz]

Looks good to me, thanks! 🚀

No need to port this to main, since the 3.x artifact will be removed soon (#2924).