// If the worker is not yet running, the delegate Executor might reject our attempt to start
      // it. To preserve FIFO order and failure atomicity of rejected execution when the same
      // Runnable is executed more than once, allocate a wrapper that we know is safe to remove by
      // object identity.
      // A data structure that returned a removal handle from add() would allow eliminating this
      // allocation.
      submittedTask =

     * Returns a newly-created immutable map, using the last value for any key that was added more
     * than once. The iteration order of the returned map is the order in which entries were
     * inserted into the builder, unless {@link #orderEntriesByValue} was called, in which case
     * entries are sorted by value. If a key was added more than once, it appears in iteration order

 * therefore every method of the listener will be called at most once. N.B. The {@link State#FAILED}
 * and {@link State#TERMINATED} states are terminal states, once a service enters either of these
 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes

       *
       * - after the requireNonNull call below. (And this object has its Runnable.run override
       *   called only once, just as it has its Executor.execute override called only once.)
       *
       * - if we return immediately from `execute` (in which case we never get here)
       *

  }

  public void testExecutorOnlyCalledOnce() throws Exception {
    TestService service = new TestService();
    service.startAsync().awaitRunning();
    // It should be called once during startup.
    assertEquals(1, service.numberOfTimesExecutorCalled.get());
    for (int i = 1; i < 10; i++) {
      service.runFirstBarrier.await();
      assertEquals(i, service.numberOfTimesRunCalled.get());

    }
  }

  /**
   * Implementing classes should invoke this method once their service has stopped. It will cause
   * the service to transition from {@link State#STARTING} or {@link State#STOPPING} to {@link
   * State#TERMINATED}.
   *
   * @throws IllegalStateException if the service is not one of {@link State#STOPPING}, {@link
   *     State#STARTING}, or {@link State#RUNNING}.
   */

    assertEquals(10, (int) memoizedSupplier.get());

    // now it has
    assertEquals(1, countingSupplier.calls);

    assertEquals(10, (int) memoizedSupplier.get());

    // it still should only have executed once due to memoization
    assertEquals(1, countingSupplier.calls);
  }

  public void testMemoize() {
    memoizeTest(new CountingSupplier());
    memoizeTest(new SerializableCountingSupplier());
  }

    assertEquals(10, (int) memoizedSupplier.get());

    // now it has
    assertEquals(1, countingSupplier.calls);

    assertEquals(10, (int) memoizedSupplier.get());

    // it still should only have executed once due to memoization
    assertEquals(1, countingSupplier.calls);
  }

  public void testMemoize() {
    memoizeTest(new CountingSupplier());
    memoizeTest(new SerializableCountingSupplier());
  }

   * When multiple elements are equivalent according to {@code compareTo()}, only the first one
   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
   *
   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}

    try {
      equalsTester.addEqualityGroup((Object) null);
      fail("Should fail on null reference");
    } catch (NullPointerException e) {
    }
  }

  /** Test equalObjects after adding multiple instances at once with a null */
  public void testAddTwoEqualObjectsAtOnceWithNull() {
    try {
      equalsTester.addEqualityGroup(reference, equalObject1, null);
      fail("Should fail on null equal object");