Add test of CourseHelper methods.
user
```ruby
require 'rails_helper'

describe CourseHelper, :type => :helper do
  describe '.contribution_link' do
    it "should return a link to a user's contributions page" do
      user = build(:user)
      link = contribution_link(user)
      expect(link).to include('<a href=')
    end
  end

  describe '.user_links' do
    it "should return contrib links for multiples users" do
      build(:user).save
      build(:trained).save
      links = user_links(User.all)
      expect(links).to include('<a href=')
    end
  end

end
```
assistant