Too often considered a drastic remedy for a failure, refactoring is actually a healthy practice that improves the software while the system takes its final shape, and the support for software components and the peripherals evolves through time.
Refactoring works better if all the tests are up and running on the old code. Unit tests should be adapted to the new function signatures while redesigning the module internals. On the other hand, existing functional tests for the module that is being refactored should not change if the API of the module stays unchanged, and will provide continuous feedback about the status and the accuracy of the process, as long as the interface towards other modules remains the same.
Smaller portions ...
