I have begun the work on my GSoC project, Caja-CapTP.
(If you don't know, Updoc is a test system which works by rerunning a recorded or made-up interactive session and confirming that the output is the same as before. The advantage of this system is that you can write test cases very simply as sequential code without gobs of assertFoo() for every particular attribute you think of testing.)
You can see my commits to EoJS at CIA.vc.
I am also learning more about exactly how Cajita works in areas such as library loading; the documentation in this area needs improvement, which I am going to work on myself and/or ask the Caja developers to clarify.