### Question:
ExceptionHandler { public static CompletionStage<Stage> displayExceptionPane( final String title, final String readable, final Throwable exception ) { final Pane exceptionPane = new ExceptionHandler(exception).asPane(readable); final CompletionStage<Stage> exceptionStage = Stages.stageOf(title, exceptionPane); return exceptionStage.thenCompose(Stages::scheduleDisplaying); } ExceptionHandler(final Throwable exception); Pane asPane(); Pane asPane(final String userReadableError); static Pane fromThrowable(final Throwable throwable); static CompletionStage<Stage> displayExceptionPane(
        final String title,
        final String readable,
        final Throwable exception
    );  }### Answer:
@Test public void displayExceptionPane() throws ExecutionException, InterruptedException, TimeoutException { final CompletionStage<Stage> asyncDisplayedStage = ExceptionHandler.displayExceptionPane( this.EXCEPTION_TEXT, this.EXCEPTION_TEXT_READABLE, this.EXCEPTION ); final Stage errStage = asyncDisplayedStage.toCompletableFuture().get(5, TimeUnit.SECONDS); assertThat(errStage.isShowing()).isTrue(); }