Say I have a single list of strings, and I want to perform testing on all pairs of strings except if...

# kotest

[Sebastian Schuberth]

Say I have a single list of strings, and I want to perform testing on all pairs of strings except if both strings point to the same instance. Would property testing with an Exhausive be the best way to go here, or is there something simpler?

[sam]

By strings point to the same instance, do you mean if they are equal ?

[Sebastian Schuberth]

I really only want to skip the assertion if the strings point to the same instance. I do want to perform the check if string happend to be textually equivalent, but come from different strings instances.

[Sebastian Schuberth]

Basically I just want to ensure to not compare a string to itself in the matrix of all combinations.

[sam]

I think in the JVM all equal strings share the same instance

[sam]

maybe that's only the case for literals actually

[sam]

Something like this might work for you:

val mystrings = listOf("a", "a", "b", "c")
   checkAll(Exhaustive.collection(mystrings), Exhaustive.collection(mystrings)) { a, b ->
      if (a !== b) {
         // test here
      }
   }

[Sebastian Schuberth]

ah, crap, due to string pooling, might be. then that was a bad example.

[Sebastian Schuberth]

so, if it wasn't strings, but other objects, would it then be preferable to use cartesian(myobjects, myobjects)?

[sam]

cartesian is better if you want all combinations to be tested

[Sebastian Schuberth]

so, there's no easy helper function yet to test all x-tuple permutations of a collection where it's ensured that no tuple members point to the same instance, correct?

[sam]

checkAll(Exhaustive.cartesian(mystrings.exhaustive(), mystrings.exhaustive()) { a, b -> Pair(a, b) }
   .filter { it.first != it.second }) { pairs ->

}

[sam]

correct

[sam]

I'll add some helpers now

[sam]

but they won't surface til 5.0

[Sebastian Schuberth]

ok, thanks for confirming, i just wanted to verify i'm not doing something too complicated in my code (which looks similar to yours).

[sam]

I'll add

cartesianPairs