*
   * @param expression a boolean expression
   * @param errorMessage the exception message to use if the check fails; will be converted to a
   *     string using {@link String#valueOf(Object)}
   * @throws IllegalArgumentException if {@code expression} is false
   */
  public static void checkArgument(boolean expression, @CheckForNull Object errorMessage) {
    if (!expression) {

  private final Set<E> delegate;
  private final Supplier<String> errorMessage;

  public static final <E> InvalidatableSet<E> of(
      Set<E> delegate, Supplier<Boolean> validator, Supplier<String> errorMessage) {
    return new InvalidatableSet<>(
        checkNotNull(delegate), checkNotNull(validator), checkNotNull(errorMessage));
  }

  @Override
  protected Set<E> delegate() {
    validate();

    try {
      new NullPointerTester().testMethod(bar, method);
    } catch (AssertionFailedError incorrectError) {
      String errorMessage =
          rootLocaleFormat("Should not have flagged method %s for %s", method.getName(), bar);
      assertNull(errorMessage, incorrectError);
    }
  }

  public void verifyBarFail(Method method, TwoArg bar) {
    try {

   *
   * @param expression a boolean expression
   * @param errorMessage the exception message to use if the check fails; will be converted to a
   *     string using {@link String#valueOf(Object)}
   * @throws IllegalArgumentException if {@code expression} is false
   */
  public static void checkArgument(boolean expression, @CheckForNull Object errorMessage) {
    if (!expression) {

      final AtomicReference<String> errorMessage = Atomics.newReference();
      executor.execute(
          new Runnable() {
            @Override
            public void run() {
              future.set("success");
              if (!future.isDone()) {
                errorMessage.set("Set call exited before future was complete.");
              }
            }

      final AtomicReference<String> errorMessage = Atomics.newReference();
      executor.execute(
          new Runnable() {
            @Override
            public void run() {
              future.set("success");
              if (!future.isDone()) {
                errorMessage.set("Set call exited before future was complete.");
              }
            }