How to test rack middleware

ssl_requirement_spec.rb

require 'spec_helper'

# Based on https://github.com/rails/ssl_requirement/blob/master/lib/ssl_requirement.rb
class SslRequirement
  def initialize(app, options= {})
    @app = app
    @allowed = options[:allowed]
    @required = options[:required]
  end
  
  def call(env)
    @env = env
    
    redirect_to = url_with_proper_protocol
    
    if redirect_to.is_a?(String)
      return [ 301, {"Location" => redirect_to}, [] ]
    end
    
    @app.call @env
  end
  
  def ssl_required?
    @required && host_and_path =~ @required
  end
  
  def ssl_allowed?
    @allowed && host_and_path =~ @allowed
  end
  
  private
  
    def request
      Rack::Request.new @env
    end
    
    def host_and_path
      request.host + request.fullpath
    end
    
    def url_with_proper_protocol
      return true if ssl_allowed?
      return_to = nil
            
      if ssl_required? && request.port != 443
        return_to = "https://" + host_and_path
      elsif request.port == 443 && !ssl_required?
        return_to = "http://" + host_and_path
      end
      
      return_to
    end
end

describe SslRequirement do
  let(:app) { ->(env) { [200, env, "app"] } }
  
  let :middleware do
    SslRequirement.new(app, required: /^admin.example.com/ )
  end
    
  it "redirects to secure protocol" do
    code, env = middleware.call env_for('http://admin.example.com')
    
    code.should == 301
    env['Location'].should == 'https://admin.example.com/'
  end
  
  it "shouldn't redirect for non matching ssl requirement" do
    code, env = middleware.call env_for('http://help.example.com')
    
    code.should == 200
  end
  
  it "redirects to non-secure site for non matching ssl requirement'" do
    code, env = middleware.call env_for('https://content.example.com')
    
    code.should == 301
    env["Location"].should == "http://content.example.com/"
  end
  
  it "allows certain url with secured protocol" do
    middleware = SslRequirement.new(app, allowed: /^help.example.com/ )
    
    code, env = middleware.call env_for('https://help.example.com')
    
    code.should == 200
    env["Location"].should == nil
  end
  
  def env_for url, opts={}
    Rack::MockRequest.env_for(url, opts)
  end
end