Outlaw underscores in URLs

config/routes.rb

@@ -1,3 +1,4 @@
+# For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
 Rails.application.routes.draw do
   devise_for :admin_users, {
     path: :admin,
@@ -28,12 +29,10 @@ Rails.application.routes.draw do
 
   get "/health", to: ->(_) { [204, {}, [nil]] }
 
-  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
   ActiveAdmin.routes(self)
 
   root to: "start#index"
 
-  # Content pages
   get "/accessibility-statement", to: "content#accessibility_statement"
   get "/privacy-notice", to: "content#privacy_notice"
 

spec/config/routes_spec.rb

@@ -0,0 +1,18 @@
+require "rails_helper"
+
+RSpec.describe "routes.rb" do
+  it "does not use underscores" do
+    paths = Rails.application.routes.routes.map { |r| r.path.spec.to_s if r.defaults[:controller] }.compact
+
+    # Allow underscores for ActiveAdmin, Rails and Turbo routes
+    paths = paths.reject { |p| p.starts_with?("/admin") }
+    paths = paths.reject { |p| p.starts_with?("/rails") }
+    paths = paths.reject { |p| p.include?("_historical_location") }
+
+    paths.each do |path|
+      has_underscores = path.split("/").any? { |component| !component.start_with?(":") && component.match("_") }
+
+      expect(has_underscores).to be(false), "#{path} should not have underscores"
+    end
+  end
+end