// Test convert with null text - this might throw exception
        String text = null;
        String field = "content";

        try {
            List<String> results = converter.convert(text, field, "en");
            assertNotNull(results);
        } catch (Exception e) {
            // Expected behavior - null text might cause exception
            assertNotNull(e);
        }

      Preconditions.checkNotNull(runnable, "Runnable was null.");
      Preconditions.checkNotNull(executor, "Executor was null.");

      synchronized (this) {
        if (!executed) {
          RunnableExecutorPair newTail = new RunnableExecutorPair(runnable, executor);
          if (head == null) {
            head = newTail;
            tail = newTail;
          } else {

    /** The Kerberos subject for authentication */
    private Subject subject = null;
    /** The user principal name */
    private String user = null;
    /** The Kerberos realm */
    private String realm = null;
    /** The service principal name */
    private String service = DEFAULT_SERVICE;
    /** The user credential lifetime */

    public ArtifactMetadataRetrievalException(String message) {
        this(message, null, null);
    }

    /**
     * @param cause a cause
     * @deprecated use {@link #ArtifactMetadataRetrievalException(String, Throwable, Artifact)}
     */
    @Deprecated
    public ArtifactMetadataRetrievalException(Throwable cause) {
        this(null, cause, null);
    }

    /**
     * @param message a message

     * If this method returns <code>null</code> the <code>SmbAuthException</code> that triggered the authenticator check will
     * simply be rethrown. The default implementation returns <code>null</code>.
     * @return the authentication credentials or null if none available
     */
    protected NtlmPasswordAuthenticator getNtlmPasswordAuthentication() {
        return null;
    }

     */
    protected static String getPattern(final String messageCode) {
        if (isEmpty(messageCode)) {
            return null;
        }
        final ResourceBundle resourceBundle = getResourceBundle(getSystemName(messageCode));
        if (resourceBundle == null) {
            return null;
        }

        final int length = messageCode.length();
        if (length > CODE_NUMBER_LENGTH) {

        }
    }

    // Test property filter returning null simulation
    public void test_get_filterReturnsNull() {
        // The filter.null property is configured to simulate null filter behavior
        try {
            fessConfig.get("filter.null");
            fail("Should throw exception when property is not found");
        } catch (ConfigPropertyNotFoundException e) {

    @Test
    @DisplayName("Test equals method with null netName")
    void testEqualsWithNullNetName() {
        SmbShareInfo info1 = new SmbShareInfo();
        SmbShareInfo info2 = new SmbShareInfo();

        // Both have null netName
        assertTrue(info1.equals(info2));

        SmbShareInfo info3 = new SmbShareInfo(TEST_NET_NAME, 0, TEST_REMARK);
        // One null, one non-null
        assertFalse(info1.equals(info3));

    }

    @Test
    @DisplayName("openConnection with null URL throws NullPointerException")
    void testOpenConnection_NullInput() {
        // Arrange
        Handler handler = newHandlerWith(mockCtx);

        // Act & Assert
        assertThrows(NullPointerException.class, () -> handler.openConnection(null), "Null URL should throw NPE");

        @Test
        @DisplayName("getBytes should handle null string")
        void testGetBytesWithNull() {
            // When
            byte[] result = Strings.getBytes(null, StandardCharsets.UTF_8);

            // Then
            assertNotNull(result, "Should return non-null array");
            assertEquals(0, result.length, "Should return empty array for null string");
        }

        @Test