Added tests for polymorphic belongs_to

* chore(tests): add missing test for relationships belongs_to polymorphic type definitions

* chore(tests): add missing test for relationships belongs_to polymorphic type definitions

* linting

spec/fixtures/movie.rb

@@ -3,6 +3,7 @@ class Movie
     :id,
     :name,
     :year,
+    :actor_or_user,
     :actors,
     :actor_ids,
     :polymorphics,
@@ -55,6 +56,14 @@ class MovieSerializer
   link :self, :url
 
   belongs_to :owner, serializer: UserSerializer
+
+  belongs_to :actor_or_user,
+             id_method_name: :uid,
+             polymorphic: {
+               Actor => :actor,
+               User => :user
+             }
+
   has_many(
     :actors,
     links: {

spec/integration/relationships_spec.rb

@@ -8,6 +8,7 @@ RSpec.describe FastJsonapi::ObjectSerializer do
     poly_act = Actor.fake
     poly_act.movies = [Movie.fake]
     mov.polymorphics = [User.fake, poly_act]
+    mov.actor_or_user = Actor.fake
     mov
   end
   let(:params) { {} }
@@ -93,7 +94,7 @@ RSpec.describe FastJsonapi::ObjectSerializer do
         end
       end
 
-      context 'with polymorphic' do
+      context 'with has_many polymorphic' do
         let(:params) do
           { include: ['actors_and_users.played_movies'] }
         end
@@ -121,6 +122,18 @@ RSpec.describe FastJsonapi::ObjectSerializer do
           )
         end
       end
+
+      context 'with belongs_to polymorphic' do
+        let(:params) do
+          { include: ['actor_or_user'] }
+        end
+
+        it do
+          expect(serialized['included']).to include(
+            have_type('actor').and(have_id(movie.actor_or_user.uid))
+          )
+        end
+      end
     end
   end
 end