Particularly enjoyed the emphasis on regressions. I converted to testing when working on a relatively complex data transformation. This was replacing an existing, scary data transformation process that was hard to test (we'd run new code for a few days and do a lot of manual examination), so I made extra certain to design the new system so it was testable. Catching regressions in test, especially for data processing, is just so much better than catching and repairing them in production.
Particularly enjoyed the emphasis on regressions. I converted to testing when working on a relatively complex data transformation. This was replacing an existing, scary data transformation process that was hard to test (we'd run new code for a few days and do a lot of manual examination), so I made extra certain to design the new system so it was testable. Catching regressions in test, especially for data processing, is just so much better than catching and repairing them in production.