It does depend on the nature of the code. My rule of thumb is integration code -> integration tests work better. Algorithmic/calculation code -> unit tests work

It does depend on the nature of the code. My rule of thumb is integration code -> integration tests work better. Algorithmic/calculation code -> unit tests work better. A debugger attached to an end to end test probably better if you're testing integration code. With a unit test you might have to do a lot more extra work to, e.g. construct an exact replica of a request object or a database object or something else that comes "for free" when you precisely mimic the software being used in the real world. That said, if mimicking the real world in your code is as simple as 'assert my_function("some input")' and checking the output then yea, unit tests are way quicker.