Adding headers to a request in a controller spec in RSpec 3 and Rails 4

add_headers_spec.rb

require 'rails_helper'

RSpec.describe Api::LoginsController, type: :controller do
  
  before :each do
    @header_code = 'AZSALE12345'
  end

  describe 'logout', focus: true do
    it 'returns status 204' do
      request.headers.merge!({'X-GROUP-CODE': @header_code})
      post :logout

      expect(response.status).to eq(204)
    end
  end
end