files generated by rails scaffold controller (for reference)

_form.html.erb

<%= form_for(@thing) do |f| %>
  <% if @thing.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@thing.errors.count, "error") %> prohibited this thing from being saved:</h2>

      <ul>
      <% @thing.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :source_url %><br>
    <%= f.text_area :source_url %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

agencies_controller_spec.rb

require 'rails_helper'

# This spec was generated by rspec-rails when you ran the scaffold generator.
# It demonstrates how one might use RSpec to specify the controller code that
# was generated by Rails when you ran the scaffold generator.
#
# It assumes that the implementation code is generated by the rails scaffold
# generator.  If you are using any extension libraries to generate different
# controller code, this generated spec may or may not pass.
#
# It only uses APIs available in rails and/or rspec-rails.  There are a number
# of tools you can use to make these specs even more expressive, but we're
# sticking to rails and rspec-rails APIs to keep things simple and stable.
#
# Compared to earlier versions of this generator, there is very limited use of
# stubs and message expectations in this spec.  Stubs are only used when there
# is no simpler way to get a handle on the object needed for the example.
# Message expectations are only used when there is no simpler way to specify
# that an instance is receiving a specific message.

RSpec.describe AgenciesController, :type => :controller do

  # This should return the minimal set of attributes required to create a valid
  # Agency. As you add validations to Agency, be sure to
  # adjust the attributes here as well.
  let(:valid_attributes) {
    skip("Add a hash of attributes valid for your model")
  }

  let(:invalid_attributes) {
    skip("Add a hash of attributes invalid for your model")
  }

  # This should return the minimal set of values that should be in the session
  # in order to pass any filters (e.g. authentication) defined in
  # AgenciesController. Be sure to keep this updated too.
  let(:valid_session) { {} }

  describe "GET index" do
    it "assigns all agencies as @agencies" do
      agency = Agency.create! valid_attributes
      get :index, {}, valid_session
      expect(assigns(:agencies)).to eq([agency])
    end
  end

  describe "GET show" do
    it "assigns the requested agency as @agency" do
      agency = Agency.create! valid_attributes
      get :show, {:id => agency.to_param}, valid_session
      expect(assigns(:agency)).to eq(agency)
    end
  end

  describe "GET new" do
    it "assigns a new agency as @agency" do
      get :new, {}, valid_session
      expect(assigns(:agency)).to be_a_new(Agency)
    end
  end

  describe "GET edit" do
    it "assigns the requested agency as @agency" do
      agency = Agency.create! valid_attributes
      get :edit, {:id => agency.to_param}, valid_session
      expect(assigns(:agency)).to eq(agency)
    end
  end

  describe "POST create" do
    describe "with valid params" do
      it "creates a new Agency" do
        expect {
          post :create, {:agency => valid_attributes}, valid_session
        }.to change(Agency, :count).by(1)
      end

      it "assigns a newly created agency as @agency" do
        post :create, {:agency => valid_attributes}, valid_session
        expect(assigns(:agency)).to be_a(Agency)
        expect(assigns(:agency)).to be_persisted
      end

      it "redirects to the created agency" do
        post :create, {:agency => valid_attributes}, valid_session
        expect(response).to redirect_to(Agency.last)
      end
    end

    describe "with invalid params" do
      it "assigns a newly created but unsaved agency as @agency" do
        post :create, {:agency => invalid_attributes}, valid_session
        expect(assigns(:agency)).to be_a_new(Agency)
      end

      it "re-renders the 'new' template" do
        post :create, {:agency => invalid_attributes}, valid_session
        expect(response).to render_template("new")
      end
    end
  end

  describe "PUT update" do
    describe "with valid params" do
      let(:new_attributes) {
        skip("Add a hash of attributes valid for your model")
      }

      it "updates the requested agency" do
        agency = Agency.create! valid_attributes
        put :update, {:id => agency.to_param, :agency => new_attributes}, valid_session
        agency.reload
        skip("Add assertions for updated state")
      end

      it "assigns the requested agency as @agency" do
        agency = Agency.create! valid_attributes
        put :update, {:id => agency.to_param, :agency => valid_attributes}, valid_session
        expect(assigns(:agency)).to eq(agency)
      end

      it "redirects to the agency" do
        agency = Agency.create! valid_attributes
        put :update, {:id => agency.to_param, :agency => valid_attributes}, valid_session
        expect(response).to redirect_to(agency)
      end
    end

    describe "with invalid params" do
      it "assigns the agency as @agency" do
        agency = Agency.create! valid_attributes
        put :update, {:id => agency.to_param, :agency => invalid_attributes}, valid_session
        expect(assigns(:agency)).to eq(agency)
      end

      it "re-renders the 'edit' template" do
        agency = Agency.create! valid_attributes
        put :update, {:id => agency.to_param, :agency => invalid_attributes}, valid_session
        expect(response).to render_template("edit")
      end
    end
  end

  describe "DELETE destroy" do
    it "destroys the requested agency" do
      agency = Agency.create! valid_attributes
      expect {
        delete :destroy, {:id => agency.to_param}, valid_session
      }.to change(Agency, :count).by(-1)
    end

    it "redirects to the agencies list" do
      agency = Agency.create! valid_attributes
      delete :destroy, {:id => agency.to_param}, valid_session
      expect(response).to redirect_to(agencies_url)
    end
  end

end

agencies_routing_spec.rb

require "rails_helper"

RSpec.describe AgenciesController, :type => :routing do
  describe "routing" do

    it "routes to #index" do
      expect(:get => "/agencies").to route_to("agencies#index")
    end

    it "routes to #new" do
      expect(:get => "/agencies/new").to route_to("agencies#new")
    end

    it "routes to #show" do
      expect(:get => "/agencies/1").to route_to("agencies#show", :id => "1")
    end

    it "routes to #edit" do
      expect(:get => "/agencies/1/edit").to route_to("agencies#edit", :id => "1")
    end

    it "routes to #create" do
      expect(:post => "/agencies").to route_to("agencies#create")
    end

    it "routes to #update" do
      expect(:put => "/agencies/1").to route_to("agencies#update", :id => "1")
    end

    it "routes to #destroy" do
      expect(:delete => "/agencies/1").to route_to("agencies#destroy", :id => "1")
    end

  end
end

agencies_spec.rb

require 'rails_helper'

RSpec.describe "Agencies", :type => :request do
  describe "GET /agencies" do
    it "works! (now write some real specs)" do
      get agencies_path
      expect(response).to have_http_status(200)
    end
  end
end

edit.html.erb

<h1>Editing thing</h1>

<%= render 'form' %>

<%= link_to 'Show', @thing %> |
<%= link_to 'Back', things_path %>

index.html.erb_spec.rb

require 'rails_helper'

RSpec.describe "agencies/index", :type => :view do
  before(:each) do
    assign(:agencies, [
      Agency.create!(),
      Agency.create!()
    ])
  end

  it "renders a list of agencies" do
    render
  end
end

index.json.builder

json.array!(@agencies) do |agency|
  json.extract! agency, :id
  json.url agency_url(agency, format: :json)
end

show.html.erb

<p id="notice"><%= notice %></p>

<%= link_to 'Edit', edit_thing_path(@thing) %> |
<%= link_to 'Back', things_path %>

show.html.erb_spec.rb

require 'rails_helper'

RSpec.describe "agencies/show", :type => :view do
  before(:each) do
    @agency = assign(:agency, Agency.create!())
  end

  it "renders attributes in <p>" do
    render
  end
end

show.json.builder

json.extract! @agency, :id, :created_at, :updated_at

things_controller.rb

class ThingsController < ApplicationController
  before_action :set_thing, only: [:show, :edit, :update, :destroy]

  # GET /things
  def index
    @things = Thing.all
  end

  # GET /things/1
  def show
  end

  # GET /things/new
  def new
    @thing = Thing.new
  end

  # GET /things/1/edit
  def edit
  end

  # POST /things
  def create
    @thing = Thing.new(thing_params)

    if @thing.save
      redirect_to @thing, notice: 'Thing was successfully created.'
    else
      render action: 'new'
    end
  end

  # PATCH/PUT /things/1
  def update
    if @thing.update(thing_params)
      redirect_to @thing, notice: 'Thing was successfully updated.'
    else
      render action: 'edit'
    end
  end

  # DELETE /things/1
  def destroy
    @thing.destroy
    redirect_to things_url, notice: 'Thing was successfully destroyed.'
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_thing
      @thing = Thing.find(params[:id])
    end

    # Only allow a trusted parameter "white list" through.
    def thing_params
      params[:thing]
    end
end