### Question:
FindFirstStageFactory implements TerminalStageFactory<Stage.FindFirst> { @SuppressWarnings("unchecked") @Override public <I, O> TerminalStage<I, O> create(Engine engine, Stage.FindFirst stage) { Objects.requireNonNull(stage); return (TerminalStage<I, O>) INSTANCE; }  @SuppressWarnings("unchecked") @Override TerminalStage<I, O> create(Engine engine, Stage.FindFirst stage);  }### Answer:
@Test public void create() { Multi<Integer> publisher = Multi.createFrom().items(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) .emitOn(executor); Optional<Integer> optional = ReactiveStreams.fromPublisher(publisher).filter(i -> i > 5) .findFirst().run().toCompletableFuture().join(); assertThat(optional).contains(6); }
@Test public void createWithoutStage() { assertThrows(NullPointerException.class, () -> factory.create(null, null)); }