test: use Gradle wrapper for Java track

[sanderploegsma]

This updates the exercism test command to use the Gradle wrapper for exercises on the Java track.

Dependencies:

• Add a Gradle wrapper per exercise java#2657

[arlm]

Looks good to me

[ErikSchierboom]

Note that on Linux, this requires student to set the executable bit before it can work. @sanderploegsma would you still want this to be merged?

[sanderploegsma]

That's right, thanks for reminding me! To be honest I'm not sure what the right approach is here.

Right now the installation instructions on the Java track do not include the installation of Gradle and the working locally instructions point to using the Gradle wrapper. However, this already requires students on unix-based systems to set the executable bit before they can run tests locally, unless they happen to use a local installation of Gradle instead.

The ideal solution here is still to retain file permissions when downloading exercises using the CLI. I know there is an open discussion about this in #903, perhaps it's a good idea to pick that back up? It's already mentioned there, but in the Java/Kotlin world it's considered a best-practice to use the Gradle/Maven wrappers so I really think this approach should work out-of-the-box on Exercism as well.

[sanderploegsma]

Also I'd like to note that these changes at least align the Java and Kotlin tracks again. Plus, when a student is starting out with working locally and following the instructions they will:

1. Install the Exercism CLI
2. Install Java
3. Download an exercise using the CLI
4. Invoke exercism test
5. Get an error about the gradle command not being found.

With these changes step 5 will change to the ./gradlew command not being executable, which is IMO easier to address. Plus, Windows users shouldn't run into issues at all.

[ErikSchierboom]

I know there is an open discussion about this in #903, perhaps it's a good idea to pick that back up?

Yeah let's do that. Maybe for now we'll merge this?

[sanderploegsma]

Yeah let's do that 👍

[uzilan]

I'd like to suggest that you add instructions in Testing on the Java track that explain how to chmod the .gradlew file in case people are unsure why they get the error message when running the tests