This is a VERY detailed and full of examples guide by David Goichman on how to set up and run API tests using the free TestProject tool.
I liked this nicely written article by Hui Ching Lim describing what nightly builds are, why it's good to run regression tests against them and how to do it.
Note: If you can't access the full article, simply open it in a private tab.
Kiran Parajuli did a great job preparing this thorough guide on end-to-end test automation with Cypress. It shows how to set it up, write first tests, configure the CI integration and even add a BDD layer on top. I found it easy to follow thanks to the big amount of code examples.
And for more details on CI integration, here's a decent guide on Integrating Cypress with Github CI by Ifeoma Imoh.
In this article, Alan Myrvold shares some practical pieces of advice on how to rework testing layers to focus more on unit and integration tests instead of the end-to-end tests. In other words, turning the hourglass back into a pyramid.
Python is commonly used in test automation. Andy Knight spent years sharing about it and this article sums up the very best pieces that he created or found which can help you learn it, too.