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passing 0 to f returns infinity (IEEE 754)

Not arguing the point here. It's just a terrible example.

You are both correct and wrong: I want X/0 to immediately crash (fatal error) before the bad data that caused my to try to divide by zero gets propagated farther. Now that I think about it, I really want X/Y where Y is "close" to 0 to crash too.

Of course I made the above up on the spot, but it is a reasonable thing to do for some situations. Those who know floating point math are well aware that dividing by something close to zero tends to result in very large errors, vs the true answer. (particularly if the division is part of a larger calculation)

I thought you'd get NaN, not Inf. Of course I'm probably misremembering.

I think what the above returns depends on the language. In java I think there is an actual run time exception for this. The point of the original comment is to show how 100% coverage is easy to achieve but often meaningless.

There is some other more abstract concept related to the classes of input that can possibly be passed to a method. IMHO 100% coverage and "test first" have done more harm than good to the cause of automated testing.

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