1. A method of determining oil based mud contamination of a hydrocarbon fluid obtained from a wellbore during formation testing, the method comprising: receiving a reservoir model for simulating the contamination; receiving an empirical equation for computing the contamination; for a first pumping time, separately generating a simulated contamination based on the reservoir model and an empirically computed contamination based on the empirical equation; comparing the simulated contamination and the empirically computed contamination; selecting one of the reservoir model and the empirical equation as more reliable and another one as less reliable for the first pumping time; and revising the less reliable one of the reservoir model and the empirical equation based on a result of the comparing.