What is the test for a motion to vacate a guilty plea?

Fifth and finally, we observe that there is a requirement that a defendant show "reasonable diligence to succeed on a motion to vacate" under section 1016.5. (People v. Totari (2003) 111 Cal.App.4th 1202, 1208.) "'[T]he trial court may properly consider the defendant's delay in making his application, . . . if "considerable time" has elapsed between the guilty plea and the motion to withdraw the plea, [since] the burden is on the defendant to explain and justify the delay. [Citation.] The reason for requiring due diligence is obvious. Substantial prejudice to the People may result if the case must proceed to trial after a long delay.' [Citation.]" (Id. at p. 1207 [delay of 13 years in filing motion could potentially be excused where there was no evidence the defendant had been advised of the immigration consequences of his plea and promptly motioned the court for relief upon deportation].)