Scala sbt tests with Junit not running in Parallel

Question

I've some integration tests written in Scala sbt which uses Junit5. I want to run the tests within the suite in parallel, however unable to do so.

This is how my code looks like:

trait IntegrationTestBase extends AnyFunSpec with Matchers with OptionValues with Inside
  with Inspectors with ScalaFutures with BeforeAndAfter with BeforeAndAfterAll with LazyLogging

@RunWith(classOf[JUnitRunner])
class TestClass extends IntegrationTestBase with ParallelTestExecution {
  override protected def beforeAll(): Unit = {
    super.beforeAll()
    ...
  }

  override protected def afterAll(): Unit = {
    super.afterAll()
    ...
  }

  describe("Test Group 1") {
    it("some test should pass") {
      ...
    }
  }

  describe("Test Group 2") {
    it("some different test should pass") {
      ...
    }
  }
}

Currently, Test Group 2 execution starts only after Test Group 1 is completed. I want the Test Group 1 and Test Group 2 to run in parallel. What am I missing here?

Tried adding this configuration in sbt file - Test / testForkedParallel := true but no change in result.

Also tried to configure the parallel execution guide from junit5 by creating the junit-platform.properties with configuration:

junit.jupiter.execution.parallel.enabled = true
junit.jupiter.execution.parallel.mode.default = concurrent
junit.jupiter.execution.parallel.mode.classes.default = concurrent

junit.jupiter.execution.parallel.config.strategy = fixed
junit.jupiter.execution.parallel.config.fixed.parallelism = 6

But this didn't work as well.