Undefined method response when using let and subject in RSpec

Question

I tried to write some tests for the "show" action in Rails API

require 'rails_helper'

RSpec.describe AirlinesController, type: :controller do
  describe "GET #show" do
    before(:each) do
      @airline = FactoryGirl.create(:airline)
      get :show, id: @airline.id
    end

    it "should return the airline information" do
      airline_response = json_response
      expect(airline_response[:name]).to eql @airline.name
    end

    it {should respond_with :ok}
  end
end

The test passed. However, when I try to use let and subject like this

require 'rails_helper'

RSpec.describe AirlinesController, type: :controller do
  describe "GET #show" do
    let(:airline) {FactoryGirl.create(:airline)}

    subject {airline}

    before(:each) do
      get :show, id: airline.id
    end

    it "should return the airline information" do
      airline_response = json_response
      expect(airline_response[:name]).to eql airline.name
    end

    it {should respond_with :ok}
  end
end

It showed "NoMethodError undefined method `response' for ..."

This makes me confused!

Answer 1

Don't set the subject. The subject of a controller spec is the controller, not a model object. Just remove the line that sets subject and you shouldn't get that error any more.