Comment 24 for bug 239952

getFromTypeAndExtention('someType', 'someExtension') guarantees a return value that has type 'someType'. It probably shouldn't return any extensions other than 'someExtension' and the known extensions for 'someType'.

We seriously need a regression suite for this code; it's pretty fragile, and UI consumers depend on the details to get behavior right in a number of corner cases, including some security bugs... Ideally we could find someone to go through all the old bugs on this and write tests.

As for building, how are you testing your other patches to this code? Any build with --enable-tests should have xpcshell, I would think.