// Test digits
        assertTrue(CharUtil.isUrlChar('0'));
        assertTrue(CharUtil.isUrlChar('5'));
        assertTrue(CharUtil.isUrlChar('9'));
    }

    public void test_isUrlChar_commonSpecialChars() {
        // Test common special characters
        assertTrue(CharUtil.isUrlChar('.'));
        assertTrue(CharUtil.isUrlChar('-'));
        assertTrue(CharUtil.isUrlChar('*'));