Rspec test for GZIPed response - ruby-on-rails

Question

I recently enabled GZIP on my Rails 4 app following this Thoughtbot blog post and I also have added use Rack::Deflater to my config.ru file as suggested by this post. My Rails app seems to be serving compressed content, but when I test for it using RSpec the test fails because response.headers['Content-Encoding'] is nil.
Here is my application.rb:
module MyApp
class Application < Rails::Application
# Turn on GZIP compression
config.middleware.use Rack::Deflater
end
end
Here is my spec:
require 'rails_helper'
describe GeneralController, type: :controller, focus: true do
it "a visitor has a browser that supports compression" do
['deflate', 'gzip', 'deflate,gzip', 'gzip,deflate'].each do |compression_method|
get 'about', {}, {'HTTP_ACCEPT_ENCODING' => compression_method }
binding.pry
expect(response.headers['Content-Encoding']).to be
end
end
it "a visitor's browser does not support compression" do
get 'about'
expect(response.headers['Content-Encoding']).to_not be
end
end
When I run curl --head -H "Accept-Encoding: gzip" http://localhost:3000/ I get the following output:
HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-Xss-Protection: 1; mode=block
X-Content-Type-Options: nosniff
X-Ua-Compatible: chrome=1
Content-Type: text/html; charset=utf-8
Vary: Accept-Encoding
Content-Encoding: gzip
Etag: "f7e364f21dbb81b9580cd39e308a7c15"
Cache-Control: max-age=0, private, must-revalidate
X-Request-Id: 3f018f27-40ab-4a87-a836-67fdd6bd5b6e
X-Runtime: 0.067748
Server: WEBrick/1.3.1 (Ruby/2.0.0/2014-02-24)
When I load the site and look at the Network tab of the inspector I can see that the response size is smaller than before, but my test still fails. I'm not sure if I'm missing a step here with my test or if there is an issue with my implementation of Rack::Deflater.

Answer 1

As #andy-waite pointed, RSpec controller specs are not aware of middleware, but that's why, since RSpec 2.6 we have request specs.
Request specs are, according to the docs:
designed to drive behavior through the full stack
Therefore, using RSpec > 2.6 request specs, your code should look like:
require 'rails_helper'
describe GeneralController, type: :request, focus: true do
it "a visitor has a browser that supports compression" do
['deflate', 'gzip', 'deflate,gzip', 'gzip,deflate'].each do |compression_method|
get 'about', {}, {'HTTP_ACCEPT_ENCODING' => compression_method }
binding.pry
expect(response.headers['Content-Encoding']).to be
end
end
it "a visitor's browser does not support compression" do
get 'about'
expect(response.headers['Content-Encoding']).to_not be
end
end

Answer 2

RSpec controller specs are wrapped around Rails functional tests, which are not aware of middleware:
Making Rails tests aware of Rack middleware outside Rails's internal chain