assertEquals("1", "trim", StringUtil.ltrim("zzzytrim", "xyz"));
        assertEquals("2", "", StringUtil.ltrim("xyz", "xyz"));
    }

    /**
     * @throws Exception
     */
    @Test
    public void testRtrim() throws Exception {
        assertEquals("trim", StringUtil.rtrim("trimxxxx", "x"));
        assertEquals("", StringUtil.rtrim("xyz", "xyz"));
        assertEquals("trimxxxx", StringUtil.rtrim("trimxxxx", "y"));

    assertEquals("", Strings.commonPrefix("abc", ""));
    assertEquals("", Strings.commonPrefix("", "abc"));
    assertEquals("", Strings.commonPrefix("abcde", "xyz"));
    assertEquals("", Strings.commonPrefix("xyz", "abcde"));
    assertEquals("", Strings.commonPrefix("xyz", "abcxyz"));
    assertEquals("a", Strings.commonPrefix("abc", "aaaaa"));
    assertEquals("aa", Strings.commonPrefix("aa", "aaaaa"));

        System.setProperty("abc.xyz", "789");

        value = "${abc.xyz}";
        assertEquals("789", ResourceUtil.resolve(value));

        value = "${abc}${abc.xyz}";
        assertEquals("123789", ResourceUtil.resolve(value));

        value = "xxx${abc.xyz}zzz";
        assertEquals("xxx789zzz", ResourceUtil.resolve(value));

        value = "${\\$}";
        assertEquals(value, ResourceUtil.resolve(value));

        assertEquals("コンテンツ", doc.get("content_ja"));
    }

    public void test_updateDocument_noLanguageDetected() {
        Map<String, Object> doc = new HashMap<>();
        doc.put("title", "xyz");
        doc.put("content", "xyz");

        // Without a real detector, this will throw NullPointerException
        try {
            languageHelper.updateDocument(doc);

        assertFalse(protocolHelper.isValidWebProtocol("example.com"));
        assertFalse(protocolHelper.isValidWebProtocol(""));
        assertFalse(protocolHelper.isValidWebProtocol("xyz"));
    }

    public void test_isValidFileProtocol_validUrls() {
        ComponentUtil.setFessConfig(new FessConfig.SimpleImpl() {
            @Override
            public String getCrawlerWebProtocols() {

            assertEquals("123", getIdMethod.invoke(crawlingConfigHelper, "W123"));
            assertEquals("abc", getIdMethod.invoke(crawlingConfigHelper, "Fabc"));
            assertEquals("xyz", getIdMethod.invoke(crawlingConfigHelper, "Dxyz"));
        } catch (Exception e) {
            fail("Failed to test getId method: " + e.getMessage());
        }
    }

        assertEquals("abc 123 ", fessXpathTransformer.removeCommentTag("abc<!-- foo1 -->123<!-- foo2 -->"));
        assertEquals("abc 123 xyz", fessXpathTransformer.removeCommentTag("abc<!-- foo1 -->123<!-- foo2 -->xyz"));
        assertEquals("abc ", fessXpathTransformer.removeCommentTag("abc<!---->"));
        assertEquals("abc -->", fessXpathTransformer.removeCommentTag("abc<!-- foo-->-->"));