enhance unit tests

Signed-off-by: Billy Zha <[email protected]>

cmd/oras/internal/fileref/unix.go

@@ -23,16 +23,10 @@ import (
 )
 
 // Parse parses file reference on unix.
-func Parse(reference string, defaultMediaType string) (filePath, mediaType string, err error) {
-	filePath = reference
-	mediaType = defaultMediaType
-
+func Parse(reference string, mediaType string) (filePath, mediatype string) {
 	i := strings.LastIndex(reference, ":")
-	if i >= 0 {
-		filePath, mediaType = reference[:i], reference[i+1:]
-	}
-	if filePath == "" {
-		return "", "", fmt.Errorf("found empty file path in %q", reference)
+	if i < 0 {
+		return reference, mediaType
 	}
-	return filePath, mediaType, nil
+	return reference[:i], reference[i+1:]
 }

cmd/oras/internal/fileref/unix_test.go

@@ -68,7 +68,7 @@ func TestParse(t *testing.T) {
 		wantErr       bool
 	}{
 
-		{"empty file name", args{"", ""}, "", "", true},
+		{"no input", args{"", ""}, "", "", false},
 		{"empty file name and media type", args{":", ""}, "", "", true},
 		{"empty file name with media type", args{":a", "b"}, "", "", true},
 	}

cmd/oras/internal/fileref/windows.go

@@ -25,6 +25,11 @@ import (
 
 // Parse parses file reference on windows.
 func Parse(reference string, defaultMediaType string) (filePath, mediaType string, err error) {
+	if reference == "" {
+		// no input
+		return "", "", nil
+	}
+
 	filePath, mediaType = doParse(reference, defaultMediaType)
 	if filePath == "" {
 		return "", "", fmt.Errorf("found empty file path in %q", reference)

cmd/oras/internal/fileref/windows_test.go

@@ -82,6 +82,7 @@ func TestParse(t *testing.T) {
 		wantMediatype string
 		wantErr       bool
 	}{
+		{"no input", args{"", ""}, "", "", false},
 		{"empty file name", args{":", ""}, "", "", true},
 		{"reserved character1 in file name", args{"<", "a"}, "", "", true},
 		{"reserved character2 in file name", args{">", "a"}, "", "", true},