Testing Library: https://testing-library.com/docs/angular-testing-library/intro/ Terrible name, great library More on reddit.com

Whenever asking for best practises you should always refer to Angular’s official documentation which does have an exact section for unit testing and folder structure. Check out angular.dev/guide/testing for the easiest way, once you understand the basics then I would implement Jest to replace Angular’s default of Karma. There are a few common ways but the primary way is house the .spec.ts file right next to the file it is testing. This makes it really easy to tell if a class is tested or not. However, I personally prefer to make a /tests/ folder and shove all .spec.ts files in for that given component and any other classes in the same directory. Theres not really a right or wrong answer here, best thing to do is ensure all contributors agree no matter the approach. More on reddit.com

Generally you don't want to test private methods directly. Instantiate your component and call the public ngOnInit method and then check to see if the things that the private method are supposed to do, e.g. set that class variable, happened by expecting on their value. More on reddit.com

Yes, using karma for testing is easy as it ships with the angular cli and is straightforward to use. I honestly don't test everything, just complex business logic that needs to be right and basic component rendering. I don't really test/mock http requests as those should just return correctly and/or be part of e2e testing. Having FE unit tests is just as important as having BE unit tests - last thing you want is to do a "minor" update only to find you've broken some business logic by accidentally mutating a value. More on reddit.com