f, err := fs.OpenFile(fmt.Sprintf("%s/file%d", dir, j), os.O_WRONLY|os.O_CREATE, 0)
c.Assert(err, check.IsNil)
defer f.Close()
f, err := fs.OpenFile(fmt.Sprintf("%s/file%d", dir, j), os.O_WRONLY|os.O_CREATE, 0)
c.Assert(err, check.IsNil)
defer f.Close()