What is the test for denying a mid-trial open-ended continuance?

In reviewing the decision to deny a continuance, [o]ne factor to consider is whether a continuance would be useful. [Citation.] ( People v. Frye (1998) 18 Cal.4th 894, 1013, 77 Cal.Rptr.2d 25, 959 P.2d 183.) In Frye, we upheld the trial court's denial of a midtrial open-ended continuance sought so the defendant could seek medical treatment for his mental health issues, reasoning that the trial court could have reasonably inferred that a continuance was not likely to result in any positive change in [the] defendant's mental

[189 P.3d 894]