if err != nil {
			t.Fatal(err)
		}
	}
}

// generateUsageTestFiles create nFolders * nFiles files of size bytes each.
func generateUsageTestFiles(t *testing.T, base, bucket string, nFolders, nFiles, size int) {
	pl := make([]byte, size)
	for i := range nFolders {
		name := filepath.Join(base, bucket, fmt.Sprint(i), "0.txt")