Agreed. I tend to do the following to test any application that requires a high level of quality. 1. Unit tests - for regression testing and to enforce a clean

Agreed. I tend to do the following to test any application that requires a high level of quality. 1. Unit tests - for regression testing and to enforce a clean design 2. Integration testing against real data - To check that there are no obvious bugs caused by bad interfaces or data 3. Smoke tests - To ensure that the core functionality works as expected They also get updated in terms of frequency in that order. Smoke tests take the most effort to make, but they deliver the most value so long as they have supporting unit and integration tests which catch obvious errors.