fix with_routing when testing api only controllers

actionpack/CHANGELOG.md

+*   Make `with_routing` test helper work when testing controllers inheriting from `ActionController::API`
+
+    *Julia López*
+
 *   Use accept header in integration tests with `as: :json`
 
     Instead of appending the `format` to the request path, Rails will figure

actionpack/lib/action_dispatch/testing/assertions/routing.rb

@@ -152,8 +152,11 @@ def with_routing
           _routes = @routes
 
           @controller.singleton_class.include(_routes.url_helpers)
-          @controller.view_context_class = Class.new(@controller.view_context_class) do
-            include _routes.url_helpers
+
+          if @controller.respond_to? :view_context_class
+            @controller.view_context_class = Class.new(@controller.view_context_class) do
+              include _routes.url_helpers
+            end
           end
         end
         yield @routes

actionpack/test/controller/action_pack_assertions_test.rb

@@ -128,6 +128,16 @@ def redirect_to_top_level_named_route
   end
 end
 
+class ApiOnlyController < ActionController::API
+  def nothing
+    head :ok
+  end
+
+  def redirect_to_new_route
+    redirect_to new_route_url
+  end
+end
+
 class ActionPackAssertionsControllerTest < ActionController::TestCase
   def test_render_file_absolute_path
     get :render_file_absolute_path
@@ -170,6 +180,20 @@ def test_string_constraint
     end
   end
 
+  def test_with_routing_works_with_api_only_controllers
+    @controller = ApiOnlyController.new
+
+    with_routing do |set|
+      set.draw do
+        get "new_route", to: "api_only#nothing"
+        get "redirect_to_new_route", to: "api_only#redirect_to_new_route"
+      end
+
+      process :redirect_to_new_route
+      assert_redirected_to "http://test.host/new_route"
+    end
+  end
+
   def test_assert_redirect_to_named_route_failure
     with_routing do |set|
       set.draw do