What exactly are you testing? If you're testing how well your users can use a mobile interface using either multitap or qwerty, then it would probably be easier to test the input methods separately from the application. For instance, what are the full range of characters a user can enter in your app? Letters (upper and lower), numbers, special characters (@*,/), etc. Get that list together, then create sample inputs in the form of sentences or whatever. Then test your input methods using those samples, noting input speed, error rate, satisfaction, etc.
