Ruby does not see slim files

I am trying to make a spec tests, here is the scenario:

   scenario 'Authenticated user creates question' do
    User.create!(email: 'user@test.com', password: '1234567')

    visit new_user_session_path
    fill_in 'Email', with: 'user@test.com'
    fill_in 'Password', with: '1234567'
    click_on 'Log in'

    visit questions_path
    click_on 'Ask question'
    fill_in 'Title', with: 'Test question'
    fill_in 'Body', with: 'text text'
    click_on 'Create'

    expect(page).to have_content 'Your question successfully created.'
  end

  scenario 'Non-authenticated user tries to create question' do
    visit questions_path
    click_on 'Ask question'

    expect(page).to have_content 'You need to sign in or sign up before continuing.'
  end

end 

It gives me out an error: "QuestionsController#index is missing a template for request formats: text/html". The problem is that I have an index file but in slim format: index.html.slim And it gives me out another error if I make index file erb: " Unable to find link or button "Ask question" ". So I think that the problem is that my code cannot see slim files. In application.rb I already have this code:

 config.generators do |g|
      g.template_engine = :slim
    end 

Here is part of my gemfile:

group :development do
  gem 'slim-rails'
end

What may be the problem? Why ruby cannot see my slim files?

The problem is that you have slim-rails in the development group in your Gemfile and you're running the test environment. I can't possibly think of a scenario where you would actually want different template engines per environment.

Just move it out of the development group.

gem 'slim-rails', '~> 3.2'

Adding a version constraint is also recommended for something this mission critical if you don't want your app to suddenly break.