Yeah, you got a point there. The M-Unit tests actually explains more about what the routine does than the actual routine itself.
The example I posted above is a pure example of which ways the routine could be used. At the moment I pretty much write an "documentation essay" of some routines that I KNOW I will forget how it even works after a year - since Mumps-code is really "cryptic" sometimes and really hard to understand what it does from the get-go.
But some M-Unit Tests is a good idea for "documentation-purposes" and also to maintain the functionality of the routines, so nothing breaks in the future.
I also strive to build more "Generic" Util routines that can be re-used in other places since it goes against my philosophy that a routine/function/whatever is only being used once and never again.