Replace Upstream Test Code With Dependency

[nipafx]

#4 enabled tests to be written like in JUnit 5. Part of the implementation copy-pasted a bunch of classes from the project (see f613211 for reasons). As soon as JUnit publishes test artifacts (see junit-team/junit5#572) a proper dependency can be established and the class can be removed.

[Bukama]

As soon as JUnit publishes test artifacts (see junit-team/junit5#572) a proper dependency can be established and the class can be removed.

I asked for an update yesterday and Marc replied as this

Please upgrade to 5.4.2 or later and use junit-platform-testkit.

So we can remove the classes

[nipafx]

Great, lets do that!

[nipafx]

And thanks for following up on this! 👍

[nipafx]

I realize right now that I never considered whether Marc's answer applies to what we specifically are doing with the internal API. Did you give this a try? Maybe we should. :) If you didn't and don't want to, we can do it tomorrow on stream.

[nipafx]

We gave this a try and it looks like the API does everything we need. I'll merge #210 momentarily and then we can get to work on this. I created a proof of concept in issues/6-testkit-api. Let's do it as follows:

• replace all uses of the internal API with the new one
• open a PR, so we can have a look and see how we can improve by adding our own functionality
• write that functionality and refactor accordingly (same branch)
• another review, then we merge
• open an issue with JUnit that our API rocks harder than theirs 😁