A C.S. major would at the minimum learn to test against boundary conditions. In the case of a U.S. phone number, one would test against 000-000-0000, 999-999-9999, and also check what happens if someone puts in garbage / international numbers / parenthesis / other things like that. The 999-999-9999 test would catch this immediately.
I'd go further to say that anyone who hasn't been bitten by an integer overflow bug in the past cannot have written enough software to qualify for a CS degree, unless of course they write all their software in languages that insulate you from it. I might be biased on that one, though, since I was first bitten by this bug on 16-bit systems: you can multiply two not-especially-large numbers and overflow a 16-bit integer.
For what it's worth, many of the best programmers I know majored in electrical engineering. On the other hand, many of the best programmers I know majored in math. They are likely to know even less about the inner workings of a computer.
I'd go further to say that anyone who hasn't been bitten by an integer overflow bug in the past cannot have written enough software to qualify for a CS degree, unless of course they write all their software in languages that insulate you from it. I might be biased on that one, though, since I was first bitten by this bug on 16-bit systems: you can multiply two not-especially-large numbers and overflow a 16-bit integer.
For what it's worth, many of the best programmers I know majored in electrical engineering. On the other hand, many of the best programmers I know majored in math. They are likely to know even less about the inner workings of a computer.