return empty();
        }
        return rootNode.invalidate(relativePath, caseSensitivity, diffListener)
            .<SnapshotHierarchy>map(it -> it == rootNode
                ? this
                : new DefaultSnapshotHierarchy(it, caseSensitivity))
            .orElseGet(() -> empty(caseSensitivity));
    }

    @Override
    public SnapshotHierarchy empty() {
        return empty(caseSensitivity);

    expectContents();
  }

  // retainAll(null)

  /*
   * AbstractCollection fails the retainAll(null) test when the subject
   * collection is empty, but we'd still like to test retainAll(null) when we
   * can. We split the test into empty and non-empty cases. This allows us to
   * suppress only the former.
   */

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

  public void testConcat() {
    assertThat(Shorts.concat()).isEqualTo(EMPTY);
    assertThat(Shorts.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Shorts.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Shorts.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Shorts.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Shorts.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Shorts.concat(ARRAY1, ARRAY1, ARRAY1))

            }

            @Override
            protected String getClientIp() {
                return StringUtil.EMPTY;
            }
        };
    }

    public void test_login() {
        activityHelper.useEcsFormat = false;
        activityHelper.login(OptionalThing.empty());
        assertEquals("action:LOGIN\tuser:-\tpermissions:-", localLogMsg.get());

    public static final IsolatedArray EMPTY = empty(Object.class);
    private final Class<?> arrayType;

    public IsolatedArray(ImmutableList<Isolatable<?>> elements, Class<?> arrayType) {
        super(elements);
        this.arrayType = arrayType;
    }

    @Override
    public ValueSnapshot asSnapshot() {
        if (elements.isEmpty()) {
            return ArrayValueSnapshot.EMPTY;
        }

        if (values.length == 0) {
            // invalid?
            return new PathInfo(StringUtil.EMPTY, StringUtil.EMPTY);
        }
        if (values.length == 1) {
            return new PathInfo(StringUtil.EMPTY, values[0]);
        }
        final StringBuilder buf = new StringBuilder();
        for (int i = 0; i < values.length - 1; i++) {

  public void testConcat() {
    assertThat(Longs.concat()).isEqualTo(EMPTY);
    assertThat(Longs.concat(EMPTY)).isEqualTo(EMPTY);
    assertThat(Longs.concat(EMPTY, EMPTY, EMPTY)).isEqualTo(EMPTY);
    assertThat(Longs.concat(ARRAY1)).isEqualTo(ARRAY1);
    assertThat(Longs.concat(ARRAY1)).isNotSameInstanceAs(ARRAY1);
    assertThat(Longs.concat(EMPTY, ARRAY1, EMPTY)).isEqualTo(ARRAY1);
    assertThat(Longs.concat(ARRAY1, ARRAY1, ARRAY1))

     * @param dataCrawlStartTime The parameter value of dataCrawlStartTime. (NotNull)
     */
    public void setDataCrawlStartTime(String dataCrawlStartTime) {
        registerVariable("dataCrawlStartTime", dataCrawlStartTime);
    }

    /**
     * Set the value of dataCrawlEndTime, used in parameter comment. <br>

    /**
     * Creates an empty {@link FileCollection}
     */
    static FileCollectionInternal empty(String displayName) {
        if (FileCollectionInternal.DEFAULT_COLLECTION_DISPLAY_NAME.equals(displayName)) {
            return empty();
        } else {
            return new EmptyFileCollection(displayName);
        }
    }

    /**
     * Creates an empty {@link FileCollection}
     */

   *
   * @param separatorPattern the pattern that determines whether a subsequence is a separator. This
   *     pattern may not match the empty string.
   * @return a splitter, with default settings, that uses this pattern
   * @throws IllegalArgumentException if {@code separatorPattern} matches the empty string
   */
  @GwtIncompatible // java.util.regex
  public static Splitter on(Pattern separatorPattern) {