Pass back the custom response, if the winning strategy uses the custom\! method

Signed-off-by: José Valim <jose.valim@gmail.com>

test/integration/rack_middleware_test.rb

@@ -0,0 +1,47 @@
+require "test/test_helper"
+require "rack/test"
+
+class RackMiddlewareTest < Test::Unit::TestCase
+  include Rack::Test::Methods
+
+  def app
+    ActionController::Dispatcher.new
+  end
+
+  def warden
+    last_request.env['warden']
+  end
+
+  def with_custom_strategy
+    get '/'
+
+    Warden::Strategies.add(:custom_test) do
+      def valid?
+        true
+      end
+
+      def authenticate!
+        custom! [599, {
+            "X-Custom-Response" => "Custom response test",
+            "Content-type" => "text/plain"
+          }, "Custom response test"]
+      end
+    end
+
+    #ActionController::Dispatcher.middleware.use CustomStrategyInterceptor
+    default_strategies = warden.manager.config.default_strategies
+    warden.manager.config.default_strategies :custom_test
+    yield
+    warden.manager.config.default_strategies default_strategies
+  end
+
+  def test_custom_strategy_response
+    with_custom_strategy do
+      post('/users/sign_in')
+
+      assert_equal 599, last_response.status
+      assert_equal "Custom response test", last_response.body
+      assert_equal "Custom response test", last_response.headers["X-Custom-Response"]
+    end
+  end
+end