assertTrue(result.endsWith("bbb"));
        assertTrue(result.contains(","));
    }

    @Test
    @DisplayName("Should handle long delimiter")
    void testJoinWithLongDelimiter() {
        String longDelimiter = "=".repeat(100);
        String result = StringUtil.join(longDelimiter, "A", "B");
        assertEquals("A" + longDelimiter + "B", result);
    }

    @Test