What is the test for a motion to replace an appointed attorney?

the trial court must permit the defendant to explain the basis of his contention and to relate specific instances of the attorney's inadequate performance." ' " ' [Citations.] ' "[S]ubstitution is a matter of judicial discretion. Denial of the motion is not an abuse of discretion unless the defendant has shown that a failure to replace the appointed attorney would 'substantially impair' the defendant's right to assistance of counsel." ' " (People v. Valdez (2004) 32 Cal. 4th 73, 95; accord People v. Taylor (2010) 48 Cal.4th 574, 599.)