@Test
public void addToExistingWorkbook() {
XSSFWorkbook xssfWorkbook = new XSSFWorkbook();
xssfWorkbook.createSheet("S1");
Sheet sheet = xssfWorkbook.createSheet("S2");
Row row = sheet.createRow(1);
Cell cell = row.createCell(1);
cell.setCellValue("value 2_1_1");
SXSSFWorkbook wb = new SXSSFWorkbook(xssfWorkbook);
xssfWorkbook = (XSSFWorkbook) SXSSFITestDataProvider.instance.writeOutAndReadBack(wb);
assertTrue(wb.dispose());