[Inkscape-devel] What parts of the code should be tested?

As part of my GSoC project I'm also compiling a list of (currently untested) parts of the code that could definitely use a few (unit) tests. This list will include a few of my personal favourites, and I'm working with gcov and svn logs to determine some "objectively" interesting parts of the code. Now my question to you is:

What parts of the code do you consider to be in urgent need of testing?

Obviously the most straightforward answer is "all", but - again obviously - that is also the least interesting answer :)