Migrate remaining JUnit 4 tests to JUnit Jupiter where feasible

[sbrannen]

Overview

In #23451, we migrated most of the test suite from JUnit 4 to JUnit Jupiter; however, several tests in the spring-test module are still based on JUnit 4.

Since we are now planning to deprecate our JUnit 4 support in 7.0, we should stop using JUnit 4 where feasible.

In other words, the only remaining tests based on JUnit 4 should be tests that are required to run with JUnit 4 in order to test our JUnit 4 support.

Performing this migration will then make it easier to deprecate and finally remove our JUnit 4 support. Additionally, we should be able to simplify our Checkstyle rules by doing so.

This issue is targeted for 6.2.x in order to avoid forward-merge conflicts during the 7.0 development phase as much as possible.

Related Issues

• Migrate test suite from JUnit 4 to JUnit Jupiter #23451
• Deprecate JUnit 4 support in the Spring TestContext Framework #34794

[sbrannen]

In 49e5c84 I unfortunately overlooked several JUnit 4 based tests in the junit4 package that should be migrated to JUnit Jupiter.

I am therefore reopening this issue to address those remaining test classes.