When would the actual function body need to change in this case? These micropackages almost never break because of the actual implementation, they break because

When would the actual function body need to change in this case? These micropackages almost never break because of the actual implementation, they break because they are unpublished (like left-pad) or because they change how they are exported (like in this case). If the code is in your codebase it does not need a test.