// Verify that at max depth, less than one stack frame per submitted task was consumed
      assertThat(length - baseStackDepth).isLessThan(DIRECT_EXECUTIONS_PER_THREAD / 2);
    }
  }

  @SuppressWarnings("ObjectToString") // Intended behavior
  public void testToString() {
    Future<?> unused = serializer.submitAsync(firstCallable, directExecutor());
    TestCallable secondCallable = new TestCallable(SettableFuture.create());