Blockchain is slowly going mainstream so it's nice to see articles such as this one by Rafaela Azevedo that explains how to test it in Solidity language using the Truffle Suite tools.
Domenico Angilletta shares a lot of code examples in Ruby showing how to do API contract testing using Pact.
Note: If you can't access the full article, simply open it in a private tab.
I agree with Angie Jones that test code should be treated like production code. So this great guide on doing code reviews for automated tests can surely help in achieving that.
This is a great breakdown of possible test flakiness causes, supplemented by the triaging tips and potential fixes. By George Pirocanac from Google.
And you can also read the first part.
As a test automation engineer, you may often find yourself writing tests for already existing code. Gil Zilberfeld gives some good pieces of advice on how to do it well.