[Warning: I have not looked at the way tests, nor hyphenation are structured]
I would have thought you would need to test correct behaviour of tests with and without at least one known hyphenation setup. i.e. Specify that a particular hyphenation (e.g. english) must be available for regression testing. Have your tests able to enable or disable hyphenation, or make it available/not available. Have your tests test operation of particular hyphenation related test cases with and without hyphenation, asserting that the FO results in the area trees (or whatever) expected for that test set up. Stephen Denne.