testing_omniauth.rb

#Omniauth initializer 
module OmniAuth
  module Strategy #:nodoc:
    def initialize(app, name, *args)
      @app = app
      @name = name.to_sym
      @options = args.last.is_a?(Hash) ? args.pop : {}
      yield self if block_given?
    end
  end
end

module OmniAuth
  mattr_accessor :facebook_strategy
  @@facebook_strategy = nil
end

# config/environment.rb

middleware.use Facebook, "FOO", "BAR" do |strategy|
  OmniAuth.facebook_strategy = strategy
end

# integration test

FACEBOOK_INFO = {
  :id => '12345',
  :link => 'http://facebook.com/josevalim',
  :email => 'user@example.com',
  :first_name => 'Jose',
  :last_name => 'Valim',
  :website => 'http://blog.plataformatec.com.br'
}

ACCESS_TOKEN = {
  :access_token => "plataformatec"
}

stubs = Faraday::Adapter::Test::Stubs.new do |b|
  b.post('/oauth/access_token') { [200, {}, ACCESS_TOKEN.to_json] }
  b.get('/me?access_token=plataformatec') { [200, {}, FACEBOOK_INFO.to_json] }
end

OmniAuth.facebook_strategy.client.connection.build do |b|
  b.adapter :test, stubs
end