Rails 4.1 Mailer Previews and Devise custom emails

For those looking to preview Devise emails without using custom mailers, (but still custom emails) this is what I did:

1. Configure your app for email previewing.

2. Set up the Devise Mailer Preview class

   a. Rails ~> 4.1

   # mailer/previews/devise_mailer_preview.rb
   class Devise::MailerPreview < ActionMailer::Preview
   
     def confirmation_instructions
       Devise::Mailer.confirmation_instructions(User.first, "faketoken")
     end
   
     def reset_password_instructions
       Devise::Mailer.reset_password_instructions(User.first, "faketoken")
     end
   
     ...
   
   end
   

   b. Rails ~> 5.0

   class DeviseMailerPreview < ActionMailer::Preview
   
     ... # same setup as Rails 4 above
   

3. Restart the server