What is the test for consent given by a police officer to search a car parked in a parking lot?

In this case the controlling facts in my opinion are (1) that the search of the vehicle was made for the specific purpose of seeking a registration based upon a consent given by the defendant, and (2) that the officers would have had a perfect right under the authority of People v. Blodgett, 46 Cal.2d 114, 293 P.2d 57 to approach the vehicle and question the occupants while the car was still in its parked position. That right was not lost but was in fact reinforced by the fact that upon observing the officers, the defendants started to pull away and were stopped only a short distance from the original position. Thus the conduct of the officers in stopping the car and questioning the defendants was reasonable and proper and the consent which followed was valid and effectual.