Future<?> possiblyIgnoredError = serializer.submitAsync(firstCallable, directExecutor());
    TestCallable secondCallable = new TestCallable(Futures.<Void>immediateFuture(null));
    ListenableFuture<@Nullable Void> secondFuture =
        serializer.submitAsync(secondCallable, directExecutor());
    TestCallable thirdCallable = new TestCallable(Futures.<Void>immediateFuture(null));
    @SuppressWarnings({"unused", "nullness"})

    assertThat(runnableFuture).isInstanceOf(TrustedListenableFutureTask.class);
    assertTrue(runnableFuture.isDone());
    assertTrue(runnable.run);

    ListenableFuture<String> callableFuture = e.submit(new TestCallable());
    assertThat(callableFuture).isInstanceOf(TrustedListenableFutureTask.class);
    assertTrue(callableFuture.isDone());
    assertEquals("foo", callableFuture.get());

    TestRunnable runnable2 = new TestRunnable();

    assertThat(runnableFuture).isInstanceOf(TrustedListenableFutureTask.class);
    assertTrue(runnableFuture.isDone());
    assertTrue(runnable.run);

    ListenableFuture<String> callableFuture = e.submit(new TestCallable());
    assertThat(callableFuture).isInstanceOf(TrustedListenableFutureTask.class);
    assertTrue(callableFuture.isDone());
    assertEquals("foo", callableFuture.get());

    TestRunnable runnable2 = new TestRunnable();