Make session tests in o.e.osgi.tests independent from OSGiTest/CoreTest

[HeikoKlare]

Several session test classes in org.eclipse.osgi.tests are subclasses of either CoreTest or the OSGiTest subclass of CoreTest. This change make the test classes directly inherit from JUnit 3's TestCase to become independent of the CoreTest class. The TestCase inheritance is necessary until session tests do not rely on JUnit 3 anymore.

• Remove inheritance of CoreTest and replace OSGiTest inheritance with static imports of inherited helper methods
• Replace try-catch for actual errors with making the test method throw the exception

[github-actions]

Test Results

   24 files  ±0     24 suites  ±0   11m 27s ⏱️ -1s
2 150 tests ±0  2 105 ✅ ±0  45 💤 ±0  0 ❌ ±0 
2 194 runs  ±0  2 149 ✅ ±0  45 💤 ±0  0 ❌ ±0 

Results for commit 55cbe3f. ± Comparison against base commit 9eae0f7.

♻️ This comment has been updated with latest results.

[HannesWell]

This change make the test classes directly inherit from JUnit 3's TestCase to become independent of the CoreTest class. The TestCase inheritance is necessary until session tests do not rely on JUnit 3 anymore.

From your comment in the other PR I assume the migration to Junit-4 is too much work respectively too different to a JUnit-5 pendant so that they should be migrated to Junit-5 directly?

[HeikoKlare]

From your comment in the other PR I assume the migration to Junit-4 is too much work respectively too different to a JUnit-5 pendant so that they should be migrated to Junit-5 directly?

That's my expectation, yes. I will try to figure that out in an attempt to migrate the session test framework. First thing to do for the migration of session tests is the migration of the framework (SessionTest, SessionTestSuite and all its derivatives), as they assume a specific (JUnit-3-conforming) structure of the session test classes. So the migrating of the classes in Equinox affected by this PR to either JUnit 4 or 5 first requires an update of that framework in the Platform. This PR only removes the unnecessary inheritance hierarchy between TestCase and the actual test class to (1) allow the removal of CoreTest in Platform and (2) prepare for a later JUnit migration in which complex inheritance hierarchies are a problem anyway.