set activerecord whitelist_attributes to true

spec/models/protected_branch_spec.rb

@@ -5,6 +5,10 @@ describe ProtectedBranch do
     it { should belong_to(:project) }
   end
 
+  describe "Mass assignment" do
+    it { should_not allow_mass_assignment_of(:project_id) }
+  end
+
   describe 'Validation' do
     it { should validate_presence_of(:project_id) }
     it { should validate_presence_of(:name) }