Yes I also think this is what I should do to, unfortunately when I first wrote the code I spend most of my time working on I didn't write unit tests at the function level (all my tests are at the module level). I have been meaning to get around correcting this, but the task is now so huge I fear it would take me more than a year to write all the unit tests :(
Don't aim for 100% test coverage aim at using unit tests to develop faster and more efficiently and the test coverage stats will come automatically.
I personally need to improve my TDD, but I am quite happy with my test driven bug fixing approach. When working on a bug I first turn it into a JUnit or selenium test, and then fix the bug and make the test pass.
