Set default Execution Context in ZIO

I am trying to use a TrampolineExecutionContext in ZIO in order to test background stream subscriptions on the same thread (so I can run effect in the order I would expect).

testM("Using trampoline execution context") {
      (for {
        queue <- Queue.unbounded[String]
        _ <- ZStream
          .fromQueue(queue)
          .take(1)
          .foreach(el => ZIO.effect(println(s"In Stream $el")))
          .fork
        _ <- queue.offer("Element")
        _ <- ZIO.effect(println("Inside for comprehension")).on(trampolineExecutionContext)
      } yield {
        assert(1)(equalTo(1))
      }).on(trampolineExecutionContext)
    }

In this situation, I obtain what I would expect that is:

"In Stream Element", "Inside for comprehension"

If I remove the on(trampolineExecutionContext), I would obtain "Inside for comprehension" only because I am not joining the fiber (creating a sync point).

How can I set for the entire test the default context to be trampolineExecutionContext without repeating it every time in every call or in the important calls?

Maybe it's not exactly what you need, but you can try to override runner method of DefaultRunnableSpec and replace main context with TrampolineExecutionContext:

override def runner = {
  super.runner.withPlatform( _.withExecutor(
    Executor.fromExecutionContext(1)(
      trampolineExecutionContext
    )
  ))
}

In this case you will only need one on(trampolineExecutionContext) at the end of the test instead of two.