There are lots of benefits from assuming you can do automated testing on code you write,

Testing makes you think about the specification, what it is you are actually writing and what makes it working.

It makes you thing about writing testable code, which means you worry about things like side effects, isolation and api's

and some times, it helps you end up with automated tests :)

testing doesnt just apply to mathematical notation, lots of real world applications suddenly become easily testable when you look at them with the eyes of a tester