What is involuntary manslaughter and what is the test for it?

Voluntary manslaughter is an intentional killing (but without malice) that occurs "upon a sudden quarrel or heat of passion." ( 192, subd. (a).) "A killing that would otherwise be murder is reduced to voluntary manslaughter if the defendant [intentionally] killed a person because he acted in imperfect [unreasonable] self-defense." (CALCRIM No. 571, italics added.) Involuntary manslaughter is an unintentional killing that occurs "in the commission of an unlawful act, not amounting to a felony; or in the commission of a lawful act which might produce death, in an unlawful manner, or without due caution and circumspection." ( 192, subd. (b).) That is, involuntary manslaughter is an unintentional killing that occurs during the commission of one of three types of predicate acts: a misdemeanor offense, a lawful act, or a felony that is not inherently dangerous. (People v. Butler (2010) 187 Cal.App.4th 998, 1006.)