4 ms·

Consider a line like: value = 1 / input; You can get "100% coverage" if you test that with `input = 1`, but unless you check with `input = 0` you're missi

Consider a line like: value = 1 / input; You can get "100% coverage" if you test that with `input = 1`, but unless you check with `input = 0` you're missing a quite important logical check.

akvadrako 8y ago
Not really - internally inputs 0 and 1 use different branches.
- RussianCow 8y ago
  That's not a branch; otherwise you would have an infinite (or impossibly large) number of branches for just that one line of code. A branch is when you execute one set of code upon a given condition, and another if that condition is not met.
  - qznc 8y ago
    It depends on the language. In C it is not a branch because division by zero is undefined and not a path you consider. In Java you can argue that there are two branches. One branch that throws an exception and one that does not.
    - zaphar 8y ago
      No coverage reporting library will attempt to tell you that kind of coverage. You are essentially in violent agreement with the op but turning it into an argument by using different words for the same concept.
  - akvadrako 8y ago
    I didn't say every number is a different branch. But on many processors, divide by zero triggers an interrupt. That's semantically the same as a branch.
breckuh 8y ago
Can't you just have a NonZeroInt type?
- whyonearth 8y ago
  Only if your language supports dependent types.
  - krylon 8y ago
    In Ada, you can define integer types that only accept a given range of values.
  - tonyg 8y ago
    It's perfectly possible in languages with ordinary ADTs. data Nat = Z | S Nat data NonZeroNat = OnePlus Nat data NonZeroInt = Negative NonZeroNat | Positive NonZeroNat
    - jwatte 8y ago
      C isn't one of those languages, though.
      - tonyg 8y ago
        The analogous would be the Go-style represent-a-sum-badly-as-a-product, struct nonzero_t { int is_negative; unsigned int one_less_than_the_absolute_value; }; which, under interpretation, ranges from -(2^32) to -1 and +1 to +(2^32).

Consider a line like: value = 1 / input; You can get "100% coverage" if you test that with `input = 1`, but unless you check with `input = 0` you're missing a quite important logical check.

akvadrako 8y ago

Not really - internally inputs 0 and 1 use different branches.

RussianCow 8y ago
That's not a branch; otherwise you would have an infinite (or impossibly large) number of branches for just that one line of code. A branch is when you execute one set of code upon a given condition, and another if that condition is not met.
- qznc 8y ago
  It depends on the language. In C it is not a branch because division by zero is undefined and not a path you consider. In Java you can argue that there are two branches. One branch that throws an exception and one that does not.
  - zaphar 8y ago
    No coverage reporting library will attempt to tell you that kind of coverage. You are essentially in violent agreement with the op but turning it into an argument by using different words for the same concept.
- akvadrako 8y ago
  I didn't say every number is a different branch. But on many processors, divide by zero triggers an interrupt. That's semantically the same as a branch.

breckuh 8y ago

Can't you just have a NonZeroInt type?

whyonearth 8y ago
Only if your language supports dependent types.
- krylon 8y ago
  In Ada, you can define integer types that only accept a given range of values.
- tonyg 8y ago
  It's perfectly possible in languages with ordinary ADTs. data Nat = Z | S Nat data NonZeroNat = OnePlus Nat data NonZeroInt = Negative NonZeroNat | Positive NonZeroNat
  - jwatte 8y ago
    C isn't one of those languages, though.
    - tonyg 8y ago
      The analogous would be the Go-style represent-a-sum-badly-as-a-product, struct nonzero_t { int is_negative; unsigned int one_less_than_the_absolute_value; }; which, under interpretation, ranges from -(2^32) to -1 and +1 to +(2^32).