added tests

app/models/exercise.rb

@@ -27,7 +27,7 @@ class Exercise < ActiveRecord::Base
     ActiveRecord::Base.connection.execute("SELECT AVG(score) AS average_score FROM (SELECT MAX(score) AS score FROM submissions WHERE cause = 'submit' AND exercise_id = '#{id}' GROUP BY user_id) AS maximum_scores")[0]['average_score'].to_f.round(2)
   end
 
-  def duplicate(attributes)
+  def duplicate(attributes = {})
     exercise = dup
     exercise.attributes = attributes
     files.each { |file| exercise.files << file.dup }

spec/controllers/exercises_controller_spec.rb

@@ -5,6 +5,24 @@ describe ExercisesController do
   let(:user) { FactoryGirl.create(:admin) }
   before(:each) { allow(controller).to receive(:current_user).and_return(user) }
 
+  describe 'POST #clone' do
+    let(:request) { proc { post :clone, id: exercise.id } }
+    before(:each) { request.call }
+
+    expect_assigns(exercise: Exercise)
+
+    it 'clones the exercise' do
+      expect_any_instance_of(Exercise).to receive(:duplicate).with(hash_including(public: false, user: user)).and_call_original
+      expect { request.call }.to change(Exercise, :count).by(1)
+    end
+
+    it 'generates a new token' do
+      expect(Exercise.last.token).not_to eq(exercise.token)
+    end
+
+    expect_redirect
+  end
+
   describe 'POST #create' do
     let(:exercise_attributes) { FactoryGirl.build(:dummy).attributes }
 

spec/models/exercise_spec.rb

@@ -27,4 +27,28 @@ describe Exercise do
     expect(exercise.errors[:user_id]).to be_present
     expect(exercise.errors[:user_type]).to be_present
   end
+
+  describe '#duplicate' do
+    let(:exercise) { FactoryGirl.create(:fibonacci) }
+    after(:each) { exercise.duplicate }
+
+    it 'duplicates the exercise' do
+      expect(exercise).to receive(:dup).and_call_original
+    end
+
+    it 'overwrites the supplied attributes' do
+      title = Forgery(:basic).text
+      expect(exercise.duplicate(title: title).title).to eq(title)
+    end
+
+    it 'duplicates all associated files' do
+      exercise.files.each do
+        |file| expect(file).to receive(:dup).and_call_original
+      end
+    end
+
+    it 'returns the duplicated exercise' do
+      expect(exercise.duplicate).to be_an(Exercise)
+    end
+  end
 end