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 test_empty() {
        // Test empty user bean creation
        FessUserBean emptyBean = FessUserBean.empty();
        assertNotNull(emptyBean);

        // Test getUserId returns EMPTY_USER_ID
        assertEquals(Constants.EMPTY_USER_ID, emptyBean.getUserId());

        // Test hasRoles always returns true for empty user
        assertTrue(emptyBean.hasRoles(new String[] { "admin" }));

     *
     * @return an {@link Optional} containing the map of user properties, or empty if not set
     */
    @Nonnull
    Optional<Map<String, String>> userProperties();

    /**
     * Indicates whether to show the version information and exit.
     *
     * @return an {@link Optional} containing the boolean flag, or empty if not set
     */
    @Nonnull
    Optional<Boolean> showVersionAndExit();

    /**

    data.write("8a00".decodeHex()) // Pong
    data.write("80026c6f".decodeHex()) // lo
    clientReader.processNextFrame()
    callback.assertPong(EMPTY)
    callback.assertPong(EMPTY)
    callback.assertPong(EMPTY)
    callback.assertPong(EMPTY)
    callback.assertTextMessage("Hello")
  }

  @Test fun clientTwoFrameCompressedHelloWithPongs() {

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

        // Assert deleteByQuery was called with the configured empty index
        assertTrue(deleteByQueryCalled);
        assertEquals("", deleteIndex);

        // Assert result is empty when successful
        assertEquals("", result);
    }

    public void test_execute_withEmptyFieldName() {
        // Configure empty field name
        expiresFieldName = "";

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

     *
     * @param pattern
     *            The date pattern. Must not be {@literal null} or an empty string.
     * @param propertyNames
     *            An array of property names. Each element must not be {@literal null} or an empty string.
     * @return A {@link CopyOptions} with a date converter applied.
     * @see CopyOptions#dateConverter(String, CharSequence...)

     *
     * @return an {@link Optional} containing the list of goals, or empty if not specified
     */
    @Nonnull
    Optional<List<String>> goals();

    /**
     * Returns the target POM model version for upgrades.
     * Supported values include "4.0.0" and "4.1.0".
     *
     * @return an {@link Optional} containing the model version, or empty if not specified
     */
    @Nonnull
    Optional<String> modelVersion();