What is the test for reversal of a finding of voluntary manslaughter?

Moreover, even were we to conclude the trial court erred in failing to instruct on voluntary manslaughter based on sudden quarrel/heat of passion or imperfect self-defense, the error was plainly harmless. The failure to instruct on a lesser included offense "is not a structural defect in the proceedings, but mere misdirection of the jury...." (People v. Breverman, supra, 19 Cal.4th at p. 149.) As such, reversal is not required unless an examination of the entire cause, including the evidence, discloses that the error resulted in a miscarriage of justice. (Ibid.) "This test is not met unless it appears 'reasonably probable' the defendant would have achieved a more favorable result had the error not occurred. (People v. Watson (1956) 46 Cal.2d 818, 836....)" (Ibid.)