Isolate, Understand, Implement

Isolate, understand, implement: three very important things to remember when adding, modifying or replacing features on a project.  The first step is to isolate the feature.  Hopefully, your project is designed in such a way that once the code is isolated it is in a single place.  The next step is understand.  Meaning understand what the code currently does.  Run the unit tests.  Make sure you know without a doubt why the code works and what the code does.  Also understand any effects that your changes might have.  And finally, implement the new code or changes.  During this phase you’ll modify the unit test set as appropriate, make the necessary changes to the code base, and ensure that the application is stable before pushing it back to your repository.