indexCh <- idx
			pw.CloseWithError(err)
			return
		}
		pw.CloseWithError(comp.Close())
	}()
	var gotIdx []byte
	return pr, func() []byte {
		if gotIdx != nil {
			return gotIdx
		}
		// Will get index or nil if closed.
		gotIdx = <-indexCh
		return gotIdx
	}
}

// compressSelfTest performs a self-test to ensure that compression

		}
		for i := range xl.versions {
			hdr := xl.versions[i].header
			ver, err := xl.getIdx(i)
			if err != nil {
				t.Error(err)
				continue
			}
			gotHdr := ver.header()
			if hdr != gotHdr {
				t.Errorf("Header does not match, index: %+v != meta: %+v", hdr, gotHdr)
			}
		}
	}
	t.Run("load-legacy", func(t *testing.T) {
		var xl xlMetaV2
		err = xl.Load(data)

				out += ".incomplete"
				fmt.Println(missingAll, "bytes missing.")
			} else {
				if wantMD5 != "" {
					sum := md5.Sum(combined)
					gotMD5 := hex.EncodeToString(sum[:])
					if gotMD5 != wantMD5 {
						fmt.Println("MD5 mismatch. Expected", wantMD5, "got", gotMD5)
						out += ".mismatch"
					} else {
						fmt.Println("MD5 verified.")
						out = fmt.Sprintf("verified/%s", baseName)
					}