What is the test for police interview a suspect who has been advised of their rights?

"[I]n carrying out their interrogations the police must avoid threats of punishment for the suspect's failure to admit or confess particular facts and must avoid false promises of leniency as a reward for admission or confession. It is apparent that when the police interview a suspect, they must skate a fine line.... They are authorized to interview suspects who have been advised of their rights, but they must conduct the interview without the undue pressure that amounts to coercion and without the dishonesty and trickery that amounts to false promise." (People v. Andersen (1980) 101 Cal.App.3d 563, 576, 161 Cal.Rptr. 707.)