// removing the password again
workbook.setWorkbookPassword(null, null);
assertFalse(workbook.getCTWorkbook().getWorkbookProtection().isSetWorkbookPassword());
// removing the whole protection structure
workbook.unLock();
assertNull(workbook.getCTWorkbook().getWorkbookProtection());
// setting a null password shouldn't introduce the protection element
workbook.setRevisionsPassword(null, null);
assertNull(workbook.getCTWorkbook().getWorkbookProtection());