Thank you for your reply. But I think you are talking about customise your practice, which is different from a practice test. A test is generated automatically without such option.
I have taken 2 practice tests until now, but there are 3 passages show up in both of them. More than 150 reading comprehension questions remain in my question poll so I am sure that a complete new practice test can be generated. Could anyone tell me how can I avoid doing repeated questions next time when I take a Magoosh practice test?