What is the test for determining whether a murder is premeditated or unpremeditated?

premeditation"' an inquiry relevant to determining whether the offense is premeditated murder in the first degree, or unpremeditated murder in the second degree. [Citations.]" (People v. Carasi, supra, 44 Cal.4th at p. 1306.) "The test of whether provocation or heat of passion can negate malice so as to mitigate murder to voluntary manslaughter is objective.... The test of whether provocation or heat of passion can negate deliberation and premeditation so as to reduce first degree murder to second degree murder, on the other hand, is subjective. [Citations.]" (People v. Padilla (2002) 103 Cal.App.4th 675, 678, citations omitted.)