fstest: add ability for mock objects and filesystems to have hashes

fstest/mockfs/mockfs.go

@@ -18,6 +18,7 @@ type Fs struct {
 	root     string        // The root directory (OS path)
 	features *fs.Features  // optional features
 	rootDir  fs.DirEntries // directory listing of root
+	hashes   hash.Set      // which hashes we support
 }
 
 // ErrNotImplemented is returned by unimplemented methods
@@ -66,7 +67,12 @@ func (f *Fs) Precision() time.Duration {
 
 // Hashes returns the supported hash types of the filesystem
 func (f *Fs) Hashes() hash.Set {
-	return hash.NewHashSet()
+	return f.hashes
+}
+
+// SetHashes sets the hashes that this supports
+func (f *Fs) SetHashes(hashes hash.Set) {
+	f.hashes = hashes
 }
 
 // Features returns the optional features of this Fs

fstest/mockobject/mockobject.go

@@ -178,6 +178,20 @@ func (o *ContentMockObject) Size() int64 {
 	return int64(len(o.content))
 }
 
+// Hash returns the selected checksum of the file
+// If no checksum is available it returns ""
+func (o *ContentMockObject) Hash(ctx context.Context, t hash.Type) (string, error) {
+	hasher, err := hash.NewMultiHasherTypes(hash.NewHashSet(t))
+	if err != nil {
+		return "", err
+	}
+	_, err = hasher.Write(o.content)
+	if err != nil {
+		return "", err
+	}
+	return hasher.Sums()[t], nil
+}
+
 type readCloser struct{ io.Reader }
 
 func (r *readCloser) Close() error { return nil }