We will take a Test-Driven Development (TDD) approach and the set up Continuous Integration (CI) job to automatically run our tests on Travis CI and AppVeyor, complete with code quality and coverage reporting. We will learn about controllers, models (with PostgreSQL), error handling, and asynchronous Express middleware. Finally, we’ll complete the CI/CD pipeline by configuring automatic deploy on Heroku. It sounds like a lot, but this tutorial is aimed at beginners who are ready to try their hands on a back-end project with some level of complexity, and who may still be confused as to how all the pieces fit together in a real project.

https://www.smashingmagazine.com/2020/04/express-api-backend-project-postgresql/