Serializers spec coverage (#24017)

spec/serializers/activitypub/undo_like_serializer_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ActivityPub::UndoLikeSerializer do
+  let(:serialization) do
+    JSON.parse(
+      ActiveModelSerializers::SerializableResource.new(
+        record, serializer: described_class
+      ).to_json
+    )
+  end
+  let(:record) { Fabricate(:favourite) }
+
+  describe 'type' do
+    it 'returns correct serialized type' do
+      expect(serialization['type']).to eq('Undo')
+    end
+  end
+end