While some ``++TestRule++`` classes have the desired effect without ever being directly referenced by a test, several others do not, and there's no reason to leave them cluttering up the file if they're not in use.
This rule raises an issue when ``++Test++`` class fields of the following types aren't used by any of the test methods: ``++TemporaryFolder++``, and ``++TestName++``.
This rule also applies to the JUnit 5 equivalent classes: ``++TempDir++``, and ``++TestInfo++``.