Support Customized JUnit5 TestEngine that reads test-scenarios from .json files

Referenced from @emyklebost:

Hello. I've created a custom JUnit5 TestEngine that reads test-scenarios from .json files. I would like to run these tests in vscode using the junit-platform-console-standalone.jar without a build tool. I am able to do this manually using PowerShell, e.g.: java -jar junit-standalone.jar -cp engine.jar -f test/my.test.json

I've added the Extension Pack for Java and the following in settings.json:

{
    "java.project.referencedLibraries": [
        "engine.jar",
        "junit-standalone.jar"
    ],
}

No tests are discovered in the Testing side-bar and nothing happens when clicking Run Tests. Any suggestions?

I've created a branch with my vscode setup and some screenshots as examples: https://github.com/emyklebost/fhir-tdp/tree/vscode-integration

Start by reviewing the linked vscode-integration branch and reproducing the setup from settings.json with engine.jar, junit-standalone.jar, and test/my.test.json. Compare the manual PowerShell console command with test discovery and Run Tests in the Testing sidebar; done means the customized JUnit5 TestEngine is discovered and its JSON scenarios can be run in VS Code without a build tool.