What is the test for a Miranda rights waiver?

"Determining the validity of a Miranda rights waiver requires 'an evaluation of the defendant's state of mind' [citation] and 'inquiry into all the circumstances surrounding the interrogation' [citation]. When a juvenile's waiver is at issue, consideration must be given to factors such as 'the juvenile's age, experience, education, background, and intelligence, and . . . whether he has the capacity to understand the warnings given him, the nature of his Fifth Amendment rights, and the consequences of waiving those rights.' [Citations.]" (People v. Nelson (2012) 53 Cal.4th 367, 375.)