single file rails app and test to display json, */* returns html

json_spec.rb

require 'rails'
require 'action_controller/railtie'
require 'rspec'
require 'rack/test'

class JsonTestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: '****************************************'
  config.secret_token = '****************************************'
  config.secret_key_base = 'yup'

  config.logger = Logger.new($stdout)
  Rails.logger = config.logger

  routes.draw do
    get '/'  => 'dummy#index'
  end
end

class DummyController < ActionController::Base
  def index
    render text: 'Home'
  end
end

ENV['RAILS_ENV'] = 'test'

RSpec.configure do |conf|
  conf.include Rack::Test::Methods
end

describe "json accepts" do
  let(:app) { Rails.application }

  it "returns html by default" do
    get '/'
    last_response.body.should == "Home"
  end

  it "returns json with a */* in the accept" do
    get '/', {}, {'HTTP_ACCEPT' => "application/json, text/javascript, */*; q=0.01"}
    last_response.headers['Content-Type'].should include("application/json")
  end

  it "returns json if */* isn't specified" do
    get '/', {}, {'HTTP_ACCEPT' => "application/json"}
    last_response.headers['Content-Type'].should include("application/json")
  end
end