Junit5 Migration Part 1 - #1576

[Desislav-Petrov]

Part of the Junit5 migration preparation.

• Moves imports to static to reduce change size for future PRs
• Fixes a bug in an iterator test explained in here
• Removes any junit4 syntax like @test(expected = ) as it's not supported in junit5

[Desislav-Petrov]

@donraab @motlin hopefully this one is easier to review and is a good step towards the ultimate goal

[donraab]

Hi @Desislav-Petrov, thanks! I started taking a look and have a general question. It looks like only assertEquals and assertThrows are made static imports. Is it not necessary to make assertTrue, assertFalse, assertSame static imports as well?

[motlin]

I think we should land the three items separately. If you don't mind, I'll split this up into three separate PRs.