sample shows how you can test your custom buildSrc logic with a JUnit4 test

[abendt]

Context

While learning how to use the Kotlin DSL for Gradle I found the samples to be immensely helpful. However I missed a sample that demonstrated how to unit-test your custom logic in buildSrc with. I think other users also could benefit from some this sample.

https://github.com/gradle/kotlin-dsl/issues/1087

Contributor Checklist

• [x ] Base the PR against the develop branch
• [x ] Make sure that all commits are signed off to indicate that you agree to the terms of Developer Certificate of Origin.
• [ ] Provide integration tests to verify changes from a user perspective
• [x ] Provide unit tests to verify logic
• [ ] Ensure that tests pass locally: ./gradlew check --parallel