UrlClassifier / SafeBrowsing tests currently rely for a large part on a custom format for inserting updates for testing. This is very brittle, as illustrated by bug 744993. The initial code was written and contributed by Google, which presumably could test against their own server. We no longer have that luxury. We should make a testing setup that is capable of feeding "real" updates to the browser and test on that. This will included a minimal implementation of a SafeBrowsing protocol server.
Let's do this in the V4 tests.
This is the approach we are talking for all new unit tests (including all of the V4 unit tests). We will not re-do the existing V2 tests though.