for (char c : validChars.toCharArray()) {
            assertTrue("Character '" + c + "' should be a valid URL character", CharUtil.isUrlChar(c));
        }
    }

    public void test_isUrlChar_boundaryChars() {
        // Test boundary characters for ranges
        assertTrue(CharUtil.isUrlChar('a')); // first lowercase
        assertTrue(CharUtil.isUrlChar('z')); // last lowercase