Give JUnit 4 precedence over JUnit Platform and TestNGFor backwards compatibility, JUnit 4 takes precendence over TestNG andJUnit Platform since groovy-all ships with dependencies on both. In thelatter case, JUnit Platform is used if both junit-vintage-engine andJUnit 4 are on the classpath.
Autodetect TestFramework if none is configure explicitlyWhen the TestFramework of a Test task is not configured explicitly itused to default to `useJUnit()`. Now, the task's classpath is inspectedfor a junit-platform-engine.jar or testng.jar. If one of them is found,the task uses the JUnit Platform or TestNG to execute tests,respectively.Since we have internal dependencies on the JUnit Platform and TestNG,all Test tasks in our own build are configured to `useJUnit()` andexplicitly.