enum singleton testing impossible

[compscidr]

Currently the SessionManager uses static methods via an enum class / singleton model.

Mockito on its own can't mock the methods so testing things which uses the SessionManager is impossible. One workaround is to use PowerMockito, however, it requires Junit4, and everything now is setup to use Junit5 (Jupiter). PowerMockito does not work on Junit5, and tickets have been stalled since 2016:

• Support jUnit5 powermock/powermock#830
• Introduce extension API for providing a custom ClassLoader (e.g., for Powermock) junit-team/junit5#201

It seems to be that the junit5 team won't add support for whats needed to do it, robo electric is having a similar problem:

• Real JUnit 5 support (via extension API) robolectric/robolectric#3477
  which is stuck on teh same issue in junit5.

So, I'm not confident it will be fixed in any short order, making the fastest solution be a refactor which no longer uses the enum singleton model.

This might be a good time to also introduce dependency injection properly since it will likely require the SessionManager or something to be included in any class which uses it.

[compscidr]

Resolved by #5