cats_controller.rb

get '/cats' do
  @cats = Cat.all
  erb :index
end

get '/cats/:id' do
  @cat = Cat.find(params[:id])
  erb :show
end

post '/cats' do
  Cat.create(name: params[:name], quote: params[:quote])
  redirect '/cats'
end

cats_controller_spec.rb

require 'spec_helper'
require 'uri'

describe "CatsController" do

  describe "GET /cats/:id" do

    before do
      @cat = Cat.create(name: Faker::Name.name, quote: Faker::Hacker.say_something_smart)
      get "/cats/#{@cat.id}"
    end

    it "returns an HTTP status code of 200" do
      expect(last_response.status).to eq(200)
    end

    it "renders the page belonging to specified cat" do
      expect(last_response.body).to include("<h1>#{@cat.name}</h1>")
    end

  end

  describe "GET /cats" do

    before do
      @cat1 = Cat.create(name: Faker::Name.name, quote: Faker::Hacker.say_something_smart)
      @cat2 = Cat.create(name: Faker::Name.name, quote: Faker::Hacker.say_something_smart)
      get '/cats'
    end

    it "returns an HTTP status code of 200" do
      expect(last_response.status).to eq(200)
    end

    it "returns all cats in DB in the response body" do
      expect(last_response.body).to include(@cat1.name)
      expect(last_response.body).to include(@cat2.name)
    end

  end

  describe "POST /cats" do

    describe "if valid params" do

      before do
        @valid_params = {
          name: Faker::Name.name,
          quote: Faker::Hacker.say_something_smart
        }
        post '/cats', @valid_params
      end

      it "returns an HTTP status code of 302" do
        expect(last_response.status).to eq(302)
      end

      it "redirects the user to GET /cats" do
        expect(URI(last_response.location).path).to eq('/cats')
      end

      it "creates a new cat with given params" do
        expect(Cat.find_by(name: @valid_params[:name], quote: @valid_params[:quote])).to be_truthy
      end

    end

    describe "if invalid params" do
      xit "returns an HTTP status code of 302" do
      end
      xit "redirects to the GET /cats" do
      end
      xit "stores an error in the session" do
      end
      xit "does not create a new cat" do
      end
    end
    
    after do
      Cat.destroy_all
    end

  end

end

index.erb

<ul>
  <% @cats.each do |cat| %>
    <li>
      <h2><%= cat.name %></h2>
      <p><%= cat.quote %></p>
    </li>
  <% end %>
</ul>

show.erb

<h1><%= @cat.name %></h1>
<p><%= @cat.quote %></p>