READY,
    NOT_READY,
    DONE,
    FAILED,
  }

  @CheckForNull private T next;

  @CheckForNull
  protected abstract T computeNext();

  @CanIgnoreReturnValue
  @CheckForNull
  protected final T endOfData() {
    state = State.DONE;
    return null;
  }

  @Override
  public final boolean hasNext() {
    checkState(state != State.FAILED);
    switch (state) {
      case DONE:

      try {
        stimuli[i].executeAndCompare(reference, target);
        verify(reference.getElements());
      } catch (AssertionFailedError cause) {
        Helpers.fail(cause, "failed with stimuli " + subListCopy(stimuli, i + 1));
      }
    }
  }

  private static List<Object> subListCopy(Object[] source, int size) {
    final Object[] copy = new Object[size];

    try {
      unicodeEscaper.escape("\uD800x\uDC00");
      fail("should have failed for bad Unicode input");
    } catch (IllegalArgumentException e) {
      // pass
    }
    assertEquals("<lo><hi>", charEscaper.escape("\uDC00\uD800"));
    try {
      unicodeEscaper.escape("\uDC00\uD800");
      fail("should have failed for bad Unicode input");
    } catch (IllegalArgumentException e) {
      // pass

  }

  /**
   * Returns a {@code Future} whose result is taken from this {@code Future} or, if this {@code
   * Future} fails with the given {@code exceptionType}, from the result provided by the {@code
   * fallback}. {@link Function#apply} is not invoked until the primary input has failed, so if the
   * primary input succeeds, it is never invoked. If, during the invocation of {@code fallback}, an

   * this precaution.
   *
   * In part because Cells are relatively large, we avoid creating
   * them until they are needed.  When there is no contention, all
   * updates are made to the base field.  Upon first contention (a
   * failed CAS on base update), the table is initialized to size 2.
   * The table size is doubled upon further contention until
   * reaching the nearest power of two greater than or equal to the

        assertThrows(RuntimeException.class, () -> service.startAsync().awaitRunning());
    assertThat(e).hasCauseThat().isSameInstanceAs(exception);
    assertEquals(Service.State.FAILED, service.state());
  }

  public void testFunctionalStop_failed() {
    final Exception exception = new Exception("deliberate");
    AbstractIdleService service =
        new DefaultService() {
          @Override

      new Runnable() {
        @Override
        public void run() {}
      };
  boolean called = false;

  private void assertSingleCallWithCorrectParameters(
      Runnable command, long initialDelay, long delay, TimeUnit unit) {
    assertFalse(called); // only called once.
    called = true;
    assertEquals(INITIAL_DELAY, initialDelay);
    assertEquals(DELAY, delay);
    assertEquals(UNIT, unit);

  }

  @Override
  public final boolean hasNext() {
    checkState(state != State.FAILED);
    switch (state) {
      case DONE:
        return false;
      case READY:
        return true;
      default:
    }
    return tryToComputeNext();
  }

  private boolean tryToComputeNext() {
    state = State.FAILED; // temporary pessimism
    next = computeNext();
    if (state != State.DONE) {

        tester.numCallsToVerify,
        tester.numCallsToNewTargetIterator * STEPS);
  }

  public void testVerifyCanThrowAssertionThatFailsTest() {
    final String message = "Important info about why verify failed";
    IteratorTester<Integer> tester =
        new IteratorTester<Integer>(
            1, MODIFIABLE, newArrayList(1, 2, 3), IteratorTester.KnownOrder.KNOWN_ORDER) {
          @Override

    assertFalse(listener.healthyCalled);
  }

  /**
   * This covers a bug where if a listener was installed that would stop the manager if any service
   * fails and something failed during startup before service.start was called on all the services,
   * then awaitStopped would deadlock due to an IllegalStateException that was thrown when trying to
   * stop the timer(!).
   */