public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to
   * try to ensure that this will happen.
   *
   * <p>This is a convenience method, equivalent to:
   *
   * <pre>{@code
   * awaitDone(new FinalizationPredicate() {
   *   public boolean isDone() {

    GcFinalization.awaitClear(ref);
    assertNull(ref.get());
  }

  public void testAwaitDone_FinalizationPredicate() {
    final WeakHashMap<Object, Object> map = new WeakHashMap<>();
    map.put(new Object(), Boolean.TRUE);
    GcFinalization.awaitDone(
        new FinalizationPredicate() {
          @Override
          public boolean isDone() {
            return map.isEmpty();
          }
        });

    GcFinalization.awaitClear(ref);
    assertNull(ref.get());
  }

  public void testAwaitDone_FinalizationPredicate() {
    final WeakHashMap<Object, Object> map = new WeakHashMap<>();
    map.put(new Object(), Boolean.TRUE);
    GcFinalization.awaitDone(
        new FinalizationPredicate() {
          public boolean isDone() {
            return map.isEmpty();
          }
        });

  public interface FinalizationPredicate {
    boolean isDone();
  }

  /**
   * Waits until the given weak reference is cleared, invoking the garbage collector as necessary to
   * try to ensure that this will happen.
   *
   * <p>This is a convenience method, equivalent to:
   *
   * <pre>{@code
   * awaitDone(new FinalizationPredicate() {
   *   public boolean isDone() {

    out.close();

    // Make sure that finalize deletes the file
    out = null;

    // times out and throws RuntimeException on failure
    GcFinalization.awaitDone(
        new GcFinalization.FinalizationPredicate() {
          @Override
          public boolean isDone() {
            return !file.exists();
          }
        });
  }

    out.close();

    // Make sure that finalize deletes the file
    out = null;

    // times out and throws RuntimeException on failure
    GcFinalization.awaitDone(
        new GcFinalization.FinalizationPredicate() {
          @Override
          public boolean isDone() {
            return !file.exists();
          }
        });
  }

  }


  public void testFinalizeReferentCalled() {
    final MockReference reference = new MockReference(frq = new FinalizableReferenceQueue());

    GcFinalization.awaitDone(
        new GcFinalization.FinalizationPredicate() {
          @Override
          public boolean isDone() {
            return reference.finalizeReferentCalled;
          }
        });
  }

  }


  public void testFinalizeReferentCalled() {
    final MockReference reference = new MockReference(frq = new FinalizableReferenceQueue());

    GcFinalization.awaitDone(
        new GcFinalization.FinalizationPredicate() {
          public boolean isDone() {
            return reference.finalizeReferentCalled;
          }
        });
  }

  static class MockReference extends FinalizableWeakReference<Object> {