What is the test for unanimous verdict in a criminal case?

Under the California Constitution, a jury verdict in a criminal case must be unanimous (Cal. Const., art. I, 16), and "the jury must agree unanimously that the defendant is guilty of a specific crime." (People v. Russo (2001) 25 Cal.4th 1124, 1132 (Russo).) " 'The [unanimity] instruction is designed in part to prevent the jury from amalgamating evidence of multiple offenses, no one of which has been proved beyond a reasonable doubt, in order to conclude beyond a reasonable doubt that a defendant must have done something sufficient to convict on one count.' [Citation.] [] On the other hand, where the evidence shows only a single discrete crime but leaves room for disagreement as to exactly how that crime was committed or what the defendant's precise role was, the jury need not unanimously agree on the basis or, as the cases often put it, the 'theory' whereby the defendant is guilty. [Citation.] The crime of burglary provides a good illustration of the difference between discrete crimes, which require a unanimity instruction, and theories of the case, which do not. . . . If the evidence showed two different entries with burglarious intent, for example, one of a house on Elm Street on Tuesday and another of a house on Maple Street on Wednesday, the jury would have to unanimously find the defendant guilty of at least one of those acts. If, however, the evidence showed a single entry, but possible uncertainty as to the exact burglarious intent, that uncertainty would involve only the theory of the case and not require the unanimity instruction." (Id. at pp. 1132-1133.)