Back from hiatus

Well, the new blog seems to be up and running – and gathering modest numbers of comments already. Woo.

I’ve a bunch of mail about test suite performance to gather and refine into a follow up post, but that can wait a day or two.

In bzr we suffer from a long test suite, which we let grow while we had some other very pressing performance concerns. 2.0 fixes these concerns, and we’re finding the odd moment to address our development environment a little now.

One of the things I want to do is to radically reduce the cost of testing inside bzr; code coverage is a great way to get a broad picture of what is tested. Rather than reinvent the wheel (and I’ve written one to throw away, so far) – are there tools out there that can:

  • build a per-test coverage map
  • do it quickly
  • don’t include setUp/tearDown/cleanUp code paths in the map
  • report on the difference between two such maps (at the suite level)

The third point is possibly contentious, so I should expand on it. While code that is executed by code within the test’s run() method is – from the outside – all part-of-the-test, its not (by definition) the focus of the test. And I find focused tests substantially easier to analyse failures in, because they tend to check preconditions, poke at object state etc.

As I want this coverage map to help preserve coverage as we refactor the test suite, I don’t want to include accidental coverage in the map.