public static String trim(String input) {
        if (input == null) {
            return null;
        }
        return input.strip();
    }
@Test
    void testTrim() {
        // Test with null input
        assertNull(StringUtil.trim(null));

        // Test with an empty string
        assertEquals("", StringUtil.trim(""));

        // Test with spaces
        assertEquals("Hello, World!", StringUtil.trim("  Hello, World!  "));

        // Test with Unicode spaces
        // Unicode character for em quad (\u2001) used for demonstration
        assertEquals("Hello, World!", StringUtil.trim("\u2001Hello, World!\u2001"));

        // Test with tabs and newlines
        assertEquals("Hello, World!", StringUtil.trim("\t\nHello, World!\t\n"));

        // Test with only leading spaces
        assertEquals("Hello, World!", StringUtil.trim("   Hello, World!"));

        // Test with only trailing spaces
        assertEquals("Hello, World!", StringUtil.trim("Hello, World!  "));

        // Test with a mix of spaces and Unicode characters
        assertEquals("Hello, World!", StringUtil.trim(" \tHello, World!\u2001  "));

        // Test with a string containing only spaces and Unicode characters
        assertEquals("", StringUtil.trim("  \t\u2001  "));
    }