[loopbit]

Depends, code that was not written with testing in mind can be very difficult to cover without some major refactoring.

Adding the first tests can be a slow and painful process.

Now, once you have those few tests? Yep! Add a few tests along the ones for the new functionality every time you touch a piece of code or pick the low hanging fruit every now and again and you can get to a useful test suite in no time.