In the preface of "Python Testing with pytest" I list some reasons to use pytest, under a section called "why pytest?". Someone asked me recently, a different but related question "why NOT unittest?".

unittest is an xUnit style framework. For me, xUnit style frameworks are fatally flawed for software testing.

That's what this episode is about, my opinion of 

• "Why NOT unittest?", or more broadly, 
• "What are the fatal flaws of xUnit?"

Links:

• Python Testing with pytest, Second Edition
• unittest docs
• unittest assert methods
• xUnit - Wikipedia