Automated testing of ofexport is a bit of an issue at the moment.
I've some unit tests for the core of the tool, but a lot of problems only show up when you unleash the thing on a moderately fat database (i.e. mine).
This is good for kicking the tyres but pretty lousy for automated testing since it's in a state of continuous flux.
My plan is to add a new output AND input format - json.
When this is done I can generate a json file from a test OmniFocus project and keep it as a fixed piece of test data. I can then load it, run filters and test the outcome to my hearts content.