[wvenable]

Tests lock you down to particular design by way of the interface. If you want to fundamentally redesign something, you're likely going to have to change the tests as well.

The power of automated testing is really to ensure that nothing changes, which is great when doing bug fixes, but not so great for actually evolving software.

Ultimately it just becomes easier to add new code than it is to ever change a design that is already in place.

[dagss]

Sounds like you are writing tests at the wrong level then.

I was talking about a regression test for a fix for a bug found in production. For a typical backend, write such tests against the publicly exposed API.

If you end up breaking tests as you refactor it means that you have broken backwards compatability for others who use the API...

[wvenable]

We seem to be talking at cross-purposes here. I agree that tests enforce backwards compatibility (or compatibility in general) but they also enforce a particular design. Fundamentally redesigning something generally involves breaking the testa and the API.

To put it another way, if you never break your tests you can only ever fix bugs or add more code -- you can never remove code or redesign.