[gruffle]

Sure, in this trivial example there may not be clear benefit, but with more complicated code, operations on complicated structures, with potential state changes, etc. there are many benefits. Even in your trivial example you don't cover the correctness or correct usage of your function - since it's dynamically typed it could be called with non-integer arguments - what's the expected behaviour in those cases?

[goto11]

Static typing certainly have many benefits, just as it has a number of drawbacks. But I'm not making a general argument about static versus dynamic typing, I'm just rejecting the specific argument that static typing saves you from writing any unit tests.

[gruffle]

Nobody made the argument that static typing removes the need for unit tests. It does check for many conditions that would have to be unit tested otherwise, such as calling functions with the wrong types.