@Override
          public boolean isDone() {
            return reference.finalizeReferentCalled;
          }
        });
  }

  static class MockReference extends FinalizableWeakReference<Object> {

    volatile boolean finalizeReferentCalled;

    MockReference(FinalizableReferenceQueue frq) {
      super(new Object(), frq);
    }

    @Override
    public void finalizeReferent() {

    Callable<?> sepFrqUser = (Callable<?>) sepFrqUserC.getDeclaredConstructor().newInstance();
    WeakReference<?> finalizableWeakReference = (WeakReference<?>) sepFrqUser.call();

    GcFinalization.awaitClear(finalizableWeakReference);

    Field sepFrqUserFinalizedF = sepFrqUserC.getField("finalized");
    Semaphore finalizeCount = (Semaphore) sepFrqUserFinalizedF.get(null);