braintree.rb

if Rails.env.production?
  Braintree::Configuration.environment = Rails.env.staging? ? :sandbox : :production
  Braintree::Configuration.merchant_id = ENV["braintree_merchant_id"]
  Braintree::Configuration.public_key  = ENV["braintree_public_key"]
  Braintree::Configuration.private_key = ENV["braintree_private_key"]
else
  Braintree::Configuration.environment = :sandbox
  Braintree::Configuration.merchant_id = "<super secret>"
  Braintree::Configuration.public_key  = "<super secret>"
  Braintree::Configuration.private_key = "<super secret>"
end

braintree_test_app.rb

if Rails.env.test?
  ::Rails.application.config.middleware.use BraintreeTestApp
end

class BraintreeTestApp
  def initialize(app)
    @app = app
  end
  
  def call(env)
    @env = env
    config = Braintree::Configuration.instantiate
    if request.path =~ /\/merchants\/#{config.merchant_id}\/transparent_redirect_requests$/ 
      #proxy post to braintree
      uri = URI.parse(config.protocol + "://" + config.server + ":" + 
        config.port.to_s + request.path)
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true
      res = http.post(uri.path, request.body.read)

      if res.code == "303"
        header_hash = res.header.to_hash
        header_hash["location"].first.gsub!("http://localhost:3000/", "http://www.example.com/")
        [303, {"location" => header_hash["location"].first}, ""]
      else
        raise "unexpected response from Braintree: expected a 303"
      end
    else
      @app.call(env)
    end
  end

  def request
    @request = Rack::Request.new(@env)
  end
end

new.html.erb

<%= simple_form_for @braintree_customer, 
  :as   => :customer, 
  :url  => Braintree::TransparentRedirect.url,
  :html => {:class => "form"} do |f| %>

  <%= f.input :first_name, :required => true %>
  <%= f.input :last_name, :required => true %>
  <%= f.input :email, :required => true %>

  <%= f.fields_for :credit_card, @braintree_customer.credit_card do |cc| -%>
    <%= cc.input :number,
      :input_html => {:autocomplete => "off" },
      :wrapper_html => {:class => "credit_card_number"},
      :hint => image_tag("/images/cards_accepted.png", :alt => "MasterCard, Visa") %>
    <%= cc.input :expiration_month, :collection => 1..12,
      :required     => true,
      :wrapper_html => {:class => "expiration_month"}  %>
    <%= cc.input :expiration_year, 
      :wrapper_html => {:class => "expiration_year"},
      :collection => Time.zone.now.year..(Time.zone.now.year + 25) %>

    <%= cc.input :cvv,
      :input_html   => {:autocomplete => "off" },
      :required     => true,
      :wrapper_html => {:class => "cvv"} %>
  <%- end -%>
  
  <%= f.button :submit %>
  
<%- end -%>

schema_change.rb

add_column :accounts, :payment_processor_subscription_id, :integer