Add specs for many_to_many associations

spec/orms/sequel/models.rb

@@ -22,10 +22,22 @@
   String :label_name
 end
 
+DB.create_table :songs do
+  primary_key :id
+  String :length
+  String :title
+end
+
+DB.create_table :artists_songs do
+  foreign_key :artist_id, :artists, null: false
+  foreign_key :song_id, :songs, null: false
+end
+
 class Artist < Sequel::Model
   include Surrealist
 
   one_to_many :albums
+  many_to_many :songs
 
   json_schema { { name: String } }
 end
@@ -47,12 +59,23 @@ class Label < Sequel::Model
   json_schema { { label_name: String } }
 end
 
+class Song < Sequel::Model
+  include Surrealist
+
+  many_to_many :artists
+
+  json_schema { { title: String } }
+end
+
 7.times { |i| Artist.insert(name: "Artist #{i}", age: (18 + i * 4)) }
 
 Artist.each_with_index do |artist, i|
   artist.add_album(title: "Album #{i}", year: (1950 + i * 5))
+  2.times { |t| artist.add_song(title: "Song #{i}#{t}", length: (120 + i * 5)) }
 end
 
 Album.each_with_index do |album, i|
   Label.new(label_name: "Label #{i}", album_id: album.id).save
 end
+
+Song.each { |song| song.add_artist(Artist.last) }

spec/orms/sequel/sequel_spec.rb

@@ -256,5 +256,41 @@
         end
       end
     end
+
+    describe 'many to many' do
+      let(:subject) { Surrealist.surrealize_collection(collection) }
+
+      context 'Artist -> Songs' do
+        let(:collection) { Artist.first.songs }
+        let(:result) { [{ title: 'Song 00' }, { title: 'Song 01' }].to_json }
+
+        it { is_expected.to eq(result) }
+        it_behaves_like 'error is not raised for valid params: collection'
+        it_behaves_like 'error is raised for invalid params: collection'
+
+        context '.where' do
+          let(:collection) { Artist.where(songs: Song.last(2)) }
+          let(:result) { [name: 'Artist 6'].to_json }
+
+          it { is_expected.to eq(result) }
+        end
+      end
+
+      context 'Song -> Artists' do
+        let(:collection) { Song.first.artists }
+        let(:result) { [{ name: 'Artist 0' }, { name: 'Artist 6' }].to_json }
+
+        it { is_expected.to eq(result) }
+        it_behaves_like 'error is not raised for valid params: collection'
+        it_behaves_like 'error is raised for invalid params: collection'
+
+        context '.where' do
+          let(:collection) { Song.where(artists: Artist.first(1)) }
+          let(:result) { [{ title: 'Song 00' }, { title: 'Song 01' }].to_json }
+
+          it { is_expected.to eq(result) }
+        end
+      end
+    end
   end
 end