[ddfx]

Integration tests are much slower usually, and you are testing tons of things at the same time. Something breaks (like in that example) and you have no idea of what and why went wrong.

If you unit test properly you are unit testing the business logic, that you have to properly divide and write in a modular fashion. If you want to test a more complex scenario, just add initial conditions or behaviors. If you can't do that or don't know how to do that, then you don't know what your code is doing or your code is bad designed. And that may be the case we read above.

Tests rarely break because they help you not breaking the code and functionalities, and they are so fast and efficient on making you realizing that that you don't feel the pain of it.

I can't imagine any example where "easy to unit test" != simple

[brootstrap]

in my work with python, easy to unit tests usually makes things a bit harder. You want functional methods , not mega classes with 100s of class variables , and each class method operates on some portion of those class variables. It makes it impossible to truly isolate functionality and test it. While coding though, it is very easy to make a class and throw god knows what into the class variable space and access those variables whenever... However if we have staticmethods , not reliant on any class , just the arguments provided, and it doesnt modify any class state, the test are great. We can change/refactor our models with confidence knowing the results are all the same.