I do agree with this, and have felt it from both ends. If you need to change a core class or interface which cascades throughout the system, those unit tests a

I do agree with this, and have felt it from both ends. If you need to change a core class or interface which cascades throughout the system, those unit tests are sure nice to have. I'm not sure I'd be confident enough to change the core class without the unit tests. In that sense, lack of unit tests is momentum against change.