int initialSize = collection.size();
    assertTrue("remove(null) should return true", collection.remove(null));
    assertEquals(
        "remove(present) should decrease a collection's size by one.",
        initialSize - 1,
        collection.size());
    expectMissing((E) null);
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)

    }

    @Override
    public @Nullable Integer next(Integer value) {
      int i = value;
      return (i == Integer.MAX_VALUE) ? null : i + 1;
    }

    @Override
    public @Nullable Integer previous(Integer value) {
      int i = value;
      return (i == Integer.MIN_VALUE) ? null : i - 1;
    }

    @Override
    Integer offset(Integer origin, long distance) {
      checkNonnegative(distance, "distance");

        if (fromRepo) {
            // when model is read from repo, a stream is used, then pomFile == null
            // (has consequences in inheritance algorithm since getProjectDirectory() returns null)
            parent = parent.clone();
            parent.setPomFile(null);
            child = child.clone();
            child.setPomFile(null);
        }

        SimpleProblemCollector problems = new SimpleProblemCollector();

        "A Map's hashCode() should be the sum of those of its entries (where "
            + "a null element in an entry counts as having a hash of zero).",
        expectedHashCode,
        getMap().hashCode());
  }

  private static int hash(Entry<?, ?> e) {
    return (e.getKey() == null ? 0 : e.getKey().hashCode())
        ^ (e.getValue() == null ? 0 : e.getValue().hashCode());
  }

    assertEquals("foo", entry("foo", 1).toString());
    assertEquals("bar x 2", entry("bar", 2).toString());
  }

  public void testToStringNull() {
    assertEquals("null", entry(NE, 1).toString());
    assertEquals("null x 2", entry(NE, 2).toString());
  }

  public void testEquals() {
    assertEquals(control("foo", 1), entry("foo", 1));
    assertEquals(control("bar", 2), entry("bar", 2));

     * allowing the CAS below to succeed.
     */
    Thread currentThread = Thread.currentThread();
    if (!compareAndSet(null, currentThread)) {
      return; // someone else has run or is running.
    }

    boolean run = !isDone();
    T result = null;
    Throwable error = null;
    try {
      if (run) {
        result = runInterruptibly();

  @Override
  public void setUp() throws Exception {
    if (setUp != null) {
      setUp.run();
    }
  }

  // public so that it can be referenced in generated GWT tests.
  @Override
  public void tearDown() throws Exception {
    if (tearDown != null) {
      tearDown.run();
    }
  }

  // public so that it can be referenced in generated GWT tests.

  @Override
  public void setUp() throws Exception {
    if (setUp != null) {
      setUp.run();
    }
  }

  // public so that it can be referenced in generated GWT tests.
  @Override
  public void tearDown() throws Exception {
    if (tearDown != null) {
      tearDown.run();
    }
  }

  // public so that it can be referenced in generated GWT tests.

    // [[null, null], [null], [1, null, 2], [1, 1], [1, 2], [1], [2], [], null]
    assertThat(sorted)
        .containsExactly(
            Lists.<@Nullable Integer>newArrayList(nullInt, nullInt),
            Lists.<@Nullable Integer>newArrayList(nullInt),
            Lists.<@Nullable Integer>newArrayList(1, null, 2),
            Lists.newArrayList(1, 1),
            Lists.newArrayList(1, 2),

    // [[null, null], [null], [1, null, 2], [1, 1], [1, 2], [1], [2], [], null]
    assertThat(sorted)
        .containsExactly(
            Lists.<@Nullable Integer>newArrayList(nullInt, nullInt),
            Lists.<@Nullable Integer>newArrayList(nullInt),
            Lists.<@Nullable Integer>newArrayList(1, null, 2),
            Lists.newArrayList(1, 1),
            Lists.newArrayList(1, 2),