What is the test for a valid consent to search?

^6. "The Fourth Amendment test for a valid consent to search is that the consent be voluntary, and '[v]oluntariness is a question of fact to be determined from all the circumstances' [citation]." (Ohio v. Robinette (1996) 519 U.S. 33, 40.) The Fourth Amendment does not require that "a lawfully seized defendant must be advised that he is 'free to go' before his consent to search will be recognized as voluntary." (Id. at p. 36.) In this case, there is no contention that defendant's consent to search was involuntary.