We all know This Guy: his code is of the lowest quality. He's never really "done-done" until about the third "Done", and even then, you're all just crossing your fingers....
Is this really just a PSA for Input Sanitizing?
Why yes, Yes It Is.
Protect your code from this fucker! You know he's going to call it with all sorts of invalid parameters, because, well, His Code Sucks.
Check all parameters. Make sure the error messages that go into the exceptions explain it to Joey clearly enough that he can get it.
Don't be cryptic!
If a parameter can't be null, Say So! Use its name in the message! If the string is too short, Say So, don't leave an IndexOutOfBoundsException time-bomb just because you're lazy and it will only be called by such-and-such or everyone knows to pass zot for the blah parameter.
Joey will! You will get all sorts thrown at your code.
On the converse, when you are calling Joey's code, Be Vewy Vewy Careful....
Don't expect null-checking, or any kind of checking, because quite frankly, Joey doesn't have time or inclination for that kind of stuff; it just gets in the way of the Real Work, or he's Just Ignorant.
Either way, your strategy remains the same. Don't expect his code to tell what's wrong. Be prepared to spend tons of time in the debugger hunting down copious amounts of NullReferenceException. What Fun! Just what I want to be doing: spending most of my time in someone else's code!
But what about Tests!?
Oh, Joey either doesn't write tests, or writes completely deficient tests, e.g. only testing "success" cases and not testing any failure modes, since you know, his code doesn't throw any exceptions on purpose!
What A Fuck-Job!
Huh-huh, yeah....
PS: No Offense Personally to anyone named "Joey", unless, you know....