Ik zal nog eens een lijstje maken:

• brew install puma/puma/puma-dev
• sudo puma-dev -setup
• puma-dev -install
• mkdir ~/.puma-dev
• puma-dev link -n yourapp . from your app’s root folder
• open Firefox and go to yourapp.test
• ERROR
• open Firefox preferences
• open Privacy and Security
• all the way at the bottom you’ll find Certificates
• click on View Certificates
• in the Authorities tab, import the Puma-dev certificate which you’ll find at ~/Library/Application Support/io.puma.dev/cert.pem
• refresh yourapp.test
• GREAT SUCCESS

Natuurlijk vind je 50% van dat lijstje in de README. 👍🏻