What’s the best book you’ve ever read on unit testing concepts? Ideally something for OOP, but not necessarily a book with C# examples, could be any language. Happy time off week!
The Art of Unit Testing. It is only one I read specifically about unit testing, but it is very good.
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I haven’t read it yet, but this one by Vladimir Khorikov looks interesting.
Enterprise Craftsmanship
Highly recommend this one. It does not only teach you how to write unit tests, but it also teaches you how to write good ones.
I like The Art of Unit Testing, but I also like to promote Working Effectively with Legacy Code.

It’s not a one or the other deal, I recommend them both. TAoUT is a good introduction to what testing is and how to write new code that is more testable. WEwLC is for people who already write unit tests, but have a codebase without them to maintain. It teaches how to refactor untested code so it is testable. I personally found that taught me a lot more about writing testable code than trying to do so from scratch!

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