After a fair bit of work (feels like longer than 2 months) I’ve finally managed to get bug 382752 landed. What this gives us in simple terms is a set of functions that we can use in order to do unit testing on the extension manager. Alongside I have checked in the first unit test. Now if anything regresses bug 257155 we should know about it immediately.
Ignoring the regression detection, I’ve always found unit tests to be fantastically useful when developing new code or fixing bugs. Zipwriter is a prime example, with a large number of tests that I can run by typing a single command I can test whether the changes I have made have solved the problem and not introduced any other errors.
The next step of course is to start adding unit tests for the extension manager. I have some already in progress and hopefully soon some of the key parts of the EM should be getting checked on a daily basis.