Fix with_routing not working with get :index

lib/rspec/rails/adapters.rb

@@ -60,6 +60,48 @@ def assertion_instance
       end
     end
 
+    # @private
+    class ControllerAssertionDelegator < AssertionDelegator
+      module Setup
+        extend ActiveSupport::Concern
+
+        included { init_setup }
+
+        module ClassMethods
+          attr_reader :setup_methods, :setup_blocks
+          attr_accessor :controller_class
+
+          def init_setup
+            @setup_methods ||= []
+            @setup_blocks ||= []
+          end
+
+          def setup(*methods, &block)
+            @setup_methods += methods
+            @setup_blocks << block if block
+          end
+        end
+
+        def initialize(*)
+          super
+          self.class.controller_class = described_class
+          run_setup
+        end
+
+        def run_setup
+          self.class.setup_methods.each { |m| send(m) }
+          self.class.setup_blocks.each { |b| b.call }
+        end
+      end
+
+      def initialize(*args)
+        args << Setup
+        args << ActionDispatch::Assertions::RoutingAssertions
+        args << ActionController::TestCase::Behavior
+        super(*args)
+      end
+    end
+
     # Adapts example groups for `Minitest::Test::LifecycleHooks`
     #
     # @private

lib/rspec/rails/example/controller_example_group.rb

@@ -1,9 +1,7 @@
 module RSpec
   module Rails
     # @private
-    ControllerAssertionDelegator = RSpec::Rails::AssertionDelegator.new(
-      ActionDispatch::Assertions::RoutingAssertions
-    )
+    ControllerAssertionDelegatorInstance = RSpec::Rails::ControllerAssertionDelegator.new
 
     # @api public
     # Container module for controller spec functionality.
@@ -15,7 +13,7 @@ module ControllerExampleGroup
       include RSpec::Rails::Matchers::RedirectTo
       include RSpec::Rails::Matchers::RenderTemplate
       include RSpec::Rails::Matchers::RoutingMatchers
-      include ControllerAssertionDelegator
+      include ControllerAssertionDelegatorInstance
 
       # Class-level DSL for controller specs.
       module ClassMethods

spec/rspec/rails/example/controller_example_group_spec.rb

@@ -90,6 +90,35 @@ def my_helper
 
         example.foos_url
       end
+
+      context "when controller is not a stub" do
+        let(:custom_contoller) do
+          stub_const(
+            "CustomController",
+            Class.new(ActionController::Base) do
+              def index
+                render plain: "ok"
+              end
+            end
+          )
+        end
+
+        let(:group) { group_for custom_contoller }
+        let(:controller) { custom_contoller }
+
+        it "properly delegates routing assertions" do
+          with_isolated_stderr do
+            example.with_routing do |map|
+              map.draw do
+                get "custom" => "custom#index"
+              end
+
+              expect { example.get :index }.not_to raise_error
+            end
+          end
+        end
+      end
+
     end
 
     describe "#bypass_rescue" do