diff --git a/modules/forgefed/star_test.go b/modules/forgefed/star_test.go
new file mode 100644
index 0000000000..e6a7d8311d
--- /dev/null
+++ b/modules/forgefed/star_test.go
@@ -0,0 +1,57 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgefed
+
+import (
+	"reflect"
+	"testing"
+
+	ap "github.com/go-ap/activitypub"
+)
+
+func Test_StarMarshalJSON(t *testing.T) {
+	type testPair struct {
+		item    Star
+		want    []byte
+		wantErr error
+	}
+
+	tests := map[string]testPair{
+		"empty": {
+			item: Star{},
+			want: nil,
+		},
+		"with ID": {
+			item: Star{
+				Source: "forgejo",
+				Activity: ap.Activity{
+					ID:   "https://repo.prod.meissa.de/api/activitypub/user-id/1",
+					Type: "Star",
+					Object: ap.Object{
+						ID: "https://codeberg.org/api/activitypub/repository-id/1",
+					},
+				},
+			},
+			want: []byte(`{
+			"type": "Star",
+			"source": "forgejo",
+			"actor": "https://repo.prod.meissa.de/api/activitypub/user-id/1",
+			"object": "https://codeberg.org/api/activitypub/repository-id/1"
+		  }`),
+		},
+	}
+
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			got, err := tt.item.MarshalJSON()
+			if (err != nil || tt.wantErr != nil) && tt.wantErr.Error() != err.Error() {
+				t.Errorf("MarshalJSON() error = \"%v\", wantErr \"%v\"", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("MarshalJSON() got = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}