A new deployment has been made to a staging/UAT or production environment.
1. Test system
Run a smoke test of the main workflows of the system to ensure nothing significant has broken (e.g., user registration & login, payments, client referrals, etc).
Test the changes included in the latest deployment to ensure they’re working as expected.
Ideally, you would have written down the main workflows of the system as well as an overview of all the changes so that you can now test them one by one without having to remember what to test.
Depending on the project, you may also want to run your above tests for multiple browsers/devices/platforms using a tool like BrowserStack.
2. Notify stakeholders
Inform the relevant people of the deployment so they can also test it and provide feedback.