diff --git a/build.pl b/build.pl
index 7fd5cf839..6cfff975f 100755
--- a/build.pl
+++ b/build.pl
@@ -297,6 +297,7 @@ TARGET: lib/go/jsonsign
     - lib/go/ext/openpgp/error
 
 TARGET: lib/go/blobref
+    - lib/go/testing
 
 TARGET: lib/go/blobserver
     - lib/go/blobref
diff --git a/lib/go/blobref/blobref.go b/lib/go/blobref/blobref.go
index 8f9226755..ecf4c28d8 100644
--- a/lib/go/blobref/blobref.go
+++ b/lib/go/blobref/blobref.go
@@ -26,7 +26,7 @@ import (
 
 var kBlobRefPattern *regexp.Regexp = regexp.MustCompile(`^([a-z0-9]+)-([a-f0-9]+)$`)
 
-var supportedDigests = map[string]func()hash.Hash{
+var supportedDigests = map[string]func() hash.Hash{
 	"sha1": func() hash.Hash {
 		return sha1.New()
 	},
@@ -34,8 +34,10 @@ var supportedDigests = map[string]func()hash.Hash{
 
 // BlobRef is an immutable reference to a blob.
 type BlobRef struct {
-	hashName  string
-	digest    string
+	hashName string
+	digest   string
+
+	strValue string // "<hashname>-<digest>"
 }
 
 // SizedBlobRef is like a BlobRef but includes a (potentially mutable) size.
@@ -58,8 +60,8 @@ func (b *BlobRef) Digest() string {
 	return b.digest
 }
 
-func (o *BlobRef) String() string {
-	return fmt.Sprintf("%s-%s", o.hashName, o.digest)
+func (b *BlobRef) String() string {
+	return b.strValue
 }
 
 func (o *BlobRef) Equals(other *BlobRef) bool {
@@ -88,16 +90,23 @@ var kExpectedDigestSize = map[string]int{
 	"sha1": 40,
 }
 
+func newBlob(hashName, digest string) *BlobRef {
+	strValue := fmt.Sprintf("%s-%s", hashName, digest)
+	return &BlobRef{strValue[0:len(hashName)],
+		strValue[len(hashName)+1:],
+		strValue}
+}
+
 func blobIfValid(hashname, digest string) *BlobRef {
 	expectedSize := kExpectedDigestSize[hashname]
 	if expectedSize != 0 && len(digest) != expectedSize {
 		return nil
 	}
-	return &BlobRef{hashname, digest}
+	return newBlob(hashname, digest)
 }
 
 func FromHash(name string, h hash.Hash) *BlobRef {
-	return &BlobRef{name, fmt.Sprintf("%x", h.Sum())}
+	return newBlob(name, fmt.Sprintf("%x", h.Sum()))
 }
 
 // FromPattern takes a pattern and if it matches 's' with two exactly two valid
diff --git a/lib/go/blobref/blobref_test.go b/lib/go/blobref/blobref_test.go
index 4086fba6a..f4acbc434 100644
--- a/lib/go/blobref/blobref_test.go
+++ b/lib/go/blobref/blobref_test.go
@@ -18,10 +18,12 @@ package blobref
 
 import (
 	"testing"
+	. "camli/testing"
 )
 
 func TestAll(t *testing.T) {
- 	br := Parse("sha1-0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")
+	refStr := "sha1-0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33"
+	br := Parse(refStr)
 	if br == nil {
 		t.Fatalf("Failed to parse blobref")
 	}
@@ -31,9 +33,8 @@ func TestAll(t *testing.T) {
 	if br.digest != "0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33" {
 		t.Errorf("Invalid digest")
 	}
-	if !br.IsSupported() {
-		t.Errorf("sha1 should be supported")
-	}
+	Expect(t, br.IsSupported(), "sha1 should be supported")
+	ExpectString(t, refStr, br.String(), "String() value")
 
 	hash := br.Hash()
 	hash.Write([]byte("foo"))
@@ -47,7 +48,7 @@ func TestAll(t *testing.T) {
 }
 
 func TestNotSupported(t *testing.T) {
- 	br := Parse("unknownfunc-0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")
+	br := Parse("unknownfunc-0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33")
 	if br == nil {
 		t.Fatalf("Failed to parse blobref")
 	}
diff --git a/lib/go/blobref/fetcher.go b/lib/go/blobref/fetcher.go
index fe53dc401..352a047bd 100644
--- a/lib/go/blobref/fetcher.go
+++ b/lib/go/blobref/fetcher.go
@@ -47,5 +47,3 @@ func (df *dirFetcher) Fetch(b *BlobRef) (file ReadSeekCloser, size int64, err os
 	size = stat.Size
 	return
 }
-
-