WIP: Tags which are not allowed in a category showing in drop down.

spec/models/topic_list_spec.rb

@@ -36,4 +36,28 @@ describe TopicList do
       expect(topic_list.preloaded_custom_fields).to eq(Set.new([DiscourseTagging::TAGS_FIELD_NAME]))
     end
   end
+
+  describe '#tags' do
+    let(:tag) { Fabricate(:tag, topics: [topic]) }
+    let(:other_tag) { Fabricate(:tag, topics: [topic]) }
+
+    it 'should return the right tags' do
+      output = [tag.name, other_tag.name]
+      expect(topic_list.tags.sort).to eq(output.sort)
+    end
+
+    describe 'when topic list is filtered by category' do
+      let(:category) { Fabricate(:category) }
+      let(:topic) { Fabricate(:topic, category: category) }
+      let(:tag) { Fabricate(:tag, topics: [topic], categories: [category]) }
+      let(:topic_list) { TopicList.new('latest', topic.user, [topic], { category: category.id, category_id: category.id }) }
+
+      it 'should only return tags allowed in the category' do
+        other_tag
+        output = [tag.name]
+
+        expect(topic_list.tags).to eq(output)
+      end
+    end
+  end
 end