Test that we can open a file with WORKBOOK
FileInputStream is = new FileInputStream(dirPath + "/" + xlsA);
POIFSFileSystem fs = new POIFSFileSystem(is);
// Ensure that we have a WORKBOOK entry
fs.getRoot().getEntry("WORKBOOK");
assertTrue(true);
// Try to open the workbook
HSSFWorkbook wb = new HSSFWorkbook(fs);