What is the test for striking a strike on a conviction for violent crime?

Before striking a strike, " 'the court in question must consider whether, in light of the nature and circumstances of his present felonies and prior serious and/or violent felony convictions, and the particulars of his background, character, and prospects, the defendant may be deemed outside the scheme's spirit, in whole or in part, and hence should be treated as though he had not previously been convicted of one or more serious and/or violent felonies.' [Citation.]" (People v. Carmony (2004) 33 Cal.4th 367, 377.) There is a presumption that "any sentence that conforms to [the] sentencing norms is both rational and proper." (Id. at p. 378.) As a result, "a trial court will only abuse its discretion in failing to strike a prior felony conviction allegation in limited circumstances. For example, an abuse of discretion occurs where the trial court was not 'aware of its discretion' to dismiss [citation], or where the court considered impermissible factors in declining to dismiss [citation]." (Ibid.) The circumstances must be extraordinary before a career criminal will be deemed to fall outside the spirit of the law. (Ibid.)