public static StringBuilder print_json_diff(LogBuffer buffer, long len, String columnName, int columnIndex,
                                                String charsetName) {
        return print_json_diff(buffer, len, columnName, columnIndex, Charset.forName(charsetName));
    }
@Test
    public void print_json_diffInputNotNullZeroNotNullZeroNotNullOutputNotNull() {

        // Arrange
        final LogBuffer buffer = new LogBuffer();
        final long len = 0L;
        final String columnName = ",";
        final int columnIndex = 0;
        final String charsetName = "gbk";

        // Act
        final StringBuilder actual = JsonDiffConversion.print_json_diff(buffer,
            len,
            columnName,
            columnIndex,
            charsetName);

        // Assert result
        Assert.assertNotNull(actual);
        Assert.assertEquals(",", actual.toString());
    }