What is the test for determining whether a defendant has the ability to pay a restitution fine?

Though the trial court should consider any relevant factors in assessing the fine "including, but not limited to, the defendant's inability to pay," the "inability to pay shall not be considered a compelling and extraordinary reason not to impose a restitution fine." ( 1202.4, subds. (c)-(d).) "The court need not make express findings 'as to the factors bearing on the amount of the fine' and need not hold 'a separate hearing for the fine.' [Citation.] Unless there are '"compelling and extraordinary reasons,"' the defendant's 'lack of assets' and 'limited employment potential' are 'not germane' to his or her ability to pay the fine." (People v. Urbano (2005) 128 Cal.App.4th 396, 405.) It is presumed that a defendant has the ability to pay the fine (People v. Romero (1996) 43 Cal.App.4th 440, 448-449), and the defendant "shall bear the burden of demonstrating his or her inability to pay." ( 1202.4, subd. (d).)