testWrite{"\x00\x00", 2, nil},
			testWrite{"abc", 3, nil},
			testWrite{"\x00\x00", 2, errUnrefData},
		},
	}}

	for i, v := range vectors {
		var wantStr string
		bb := new(strings.Builder)
		w := testNonEmptyWriter{bb}
		var fw fileWriter
		switch maker := v.maker.(type) {
		case makeReg:
			fw = &regFileWriter{w, maker.size}
			wantStr = maker.wantStr
		case makeSparse:

		if !ok {
			continue
		}
		switch key {
		case "ProductVersion":
			iosVer = val
		case "BuildVersion":
			buildVer = val
		}
	}
	if iosVer == "" || buildVer == "" {
		return "", errors.New("failed to parse ideviceinfo output")
	}
	verSplit := strings.Split(iosVer, ".")
	if len(verSplit) > 2 {
		// Developer images are specific to major.minor ios version.