Refactor and tests.

spec/models/user_spec.rb

@@ -680,4 +680,22 @@ describe User do
     end
 
   end
+
+  describe "#community_participants" do
+
+    it "should return participants without duplicates" do
+      proposal = create(:proposal)
+      community = proposal.community
+      user1 = create(:user)
+      user2 = create(:user)
+
+      topic1 = create(:topic, community: community, author: user1)
+      create(:comment, commentable: topic1, author: user1)
+      create(:comment, commentable: topic1, author: user2)
+      topic2 = create(:topic, community: community, author: user2)
+
+      expect(User.community_participants(community)).to eq [user1, user2]
+    end
+  end
+
 end