Now years later this rule or guideline still holds true as we develop software (as far removed as software development from counting stock may be). For some reason it is a fundamental guideline we’re simply ignorant of. We write our code, we write our tests and thus commit the same horrendous offence. Yes, the procedure of writing unit tests as promoted in most development houses today – is flawed.
This test is a simulation of how things may behave in the real world. Inevitability things break, whether it’s caused by mechanical failure, some logical error on your part or a fellow developer which didn’t consult the documentation (or the lack thereof ) - whether you’re calling a speed sensor, making a call to a database, calling a web service or just trying to write a file to disk...