In Spring Framework 5.2, we migrated most of the test suite from JUnit
4 to JUnit Jupiter; however, prior to this commit, several tests in the
spring-test module were still based on JUnit 4 unnecessarily.
Since we are now planning to deprecate our JUnit 4 support in 7.0, this
commit migrates our remaining JUnit 4 based tests to JUnit Jupiter
whenever feasible. In the process, test classes that previously resided
under the "junit4" package have been moved to new packages directly
under the "org.springframework.text.context" package, and several
classes have been renamed for greater clarity of purpose.
Consequently, the only remaining tests based on JUnit 4 are those tests
that are required to run with JUnit 4 in order to test our JUnit 4
support.
This commit also greatly simplifies exclusions for Checkstyle rules
pertaining to JUnit usage.
See gh-23451
See gh-34794
Closes gh-34813
49e5c84928