How to test a function `fn(&str, &str) -> bool`?

[burntsushi]

How to test a function `fn(&str, &str) -> bool`?

[BurntSushi]

No. QuickCheck doesn't generate values with type &str. It is much more convenient to limit QuickCheck to owned values (or non-borrowed types that implement Copy, like ints). I don't think it's possible to write a useful implementation of Arbitrary for &str (because it needs to be able to manipulate the strings to do shrinking).

With that said, given your code here, I don't see any reason why you can't use String. If you have a String, then you can get an &str. It will cost you an allocation, but it's usually not a huge deal in this context.

I think if you s/&str/String and change edit_distance(a, b) to edit_distance(&a, &b), then it should work (assuming edit_distance accepts two values with type &str).

[febeling]

Thank you! It makes sense the way you explain it, and I'm just in the process of forming an idea what the difference between &str and String entails. With this change it works beautifully.