Add feature test for headers setup in controller specs

Author: benoittgt

features/controller_specs/headers.feature

@@ -0,0 +1,50 @@
+Feature: Headers
+
+  We recommend you to switch to request spec instead of controller spec
+  if you want to set headers in your call.
+  If you still want to set headers in controller spec, you can use
+  `request.headers` as mentioned bellow.
+
+  Scenario: Set header's value in controller spec
+    Given a file named "spec/controllers/application_controller_spec.rb" with:
+      """ruby
+      require "rails_helper"
+
+      RSpec.describe ApplicationController, :type => :controller do
+        controller do
+          def show
+            if request.headers["Authorization"] == "foo"
+              head :ok
+            else
+              head :forbidden
+            end
+          end
+        end
+
+        before do
+          routes.draw { get "show" => "anonymous#show" }
+        end
+
+        context "valid Authorization header" do
+          it "returns a 200" do
+            request.headers["Authorization"] = "foo"
+
+            get :show
+
+            expect(response).to have_http_status(:ok)
+          end
+        end
+
+        context "invalid Authorization header" do
+          it "returns a 403" do
+            request.headers["Authorization"] = "bar"
+
+            get :show
+
+            expect(response).to have_http_status(:forbidden)
+          end
+        end
+      end
+      """
+    When I run `rspec spec`
+    Then the example should pass