@Grab("org.apache.poi:poi:3.10-beta2")
@Grab("org.apache.poi:poi-ooxml:3.10-beta2")
import groovy.io.FileType
import org.apache.poi.ss.usermodel.Cell
import org.apache.poi.ss.usermodel.Row
import org.apache.poi.ss.usermodel.Sheet
import org.apache.poi.ss.usermodel.Workbook
import org.apache.poi.xssf.usermodel.XSSFFormulaEvaluator
import org.apache.poi.xssf.usermodel.XSSFWorkbook

Workbook wb = new XSSFWorkbook(new File('test.xlsx').newInputStream())
Sheet sheet = wb.getSheetAt(0)
sheet.createRow(0)
new File('testOut.xlsx').withOutputStream {wb.write(it)}