Review Emails with ActionMailer::Preview

Rails is one of my favourite frameworks, I think because it ships with a little known feature called ActionMailer::Preview, which I really want every Rails developer to know about :D

It renders your mailers & lets your preview them in the browser, which means if you want to tweak some code or totally redesign it, you can just visit http://127.0.0.1:3000/rails/mailers on your local development machine & get building.

Code Sample

# spec/mailers/previews/user_mailer_preview.rb # Preview all emails at http://localhost:3000/rails/mailers class UserMailerPreview < ActionMailer::Preview def user_welcome_notification UserMailer.user_welcome_notification(user) end private def user @user ||= FactoryBot.build(:user) end end 

FactoryBot For Sample Data

I used to use User.first as the starting point for my sample data, but I think a better approach is to use the FactoryBot factories. The main advantage is it encourages me to write better factories & increases the value for money they offer.