[actyp]

This PR restructures the test suite making it easier to extend and prepares it for some upcoming test-related PRs.

Notable Changes

• Moved tests to the packages of the classes they test.

• Migrated to JUnit 6 (Jupiter) through the junit-bom, and pinned maven-surefire-plugin.

  • JUnit 6 provides @TempDir, parameterized tests and better assertions

• Added shared test helpers to avoid repetitive code:

  • ConfigBuilders: provides config builder factories
  • FixedAlphabetBuilder: an in-memory alphabet builder
  • CliTestSupport: builds parsers and parses/asserts command-line args

• All test output now goes to @TempDir.

  • This also removed the ./output run artifacts of some RA tests.

• Removed the unused src/test/resources/default_alphabet.xml.

• The (98) tests have been maintained as previously.

[kostis]

I am not very familiar with Java testing frameworks to know why Assertions is preferable than Assert, or why Jupiter is the way forward, but I like that repetitive code is gone from the test suite and this restructuring has a leaner look and feel. (And yes, it's good that we get rid of the output dir...)