}

    @Test
    void testToString() {
        // Test toString with zterm = true
        String originalStringTrue = "HelloWorld";
        UnicodeString unicodeStringTrue = new UnicodeString(originalStringTrue, true);
        assertEquals(originalStringTrue, unicodeStringTrue.toString(), "toString should return original string with zterm");

    }

    @Test
    @DisplayName("Should join with empty string delimiter")
    void testJoinWithEmptyDelimiter() {
        String result = StringUtil.join("", "hello", "world");
        assertEquals("helloworld", result);
    }

    @Test
    @DisplayName("Should join with multi-character delimiter")
    void testJoinWithMultiCharDelimiter() {
        String result = StringUtil.join(" - ", "apple", "banana", "cherry");