What is the test for a constitutional instruction on reasonable doubt?

In Victor v. Nebraska (1994) 511 U.S. 1, 114 S.Ct. 1239, 127 L.Ed.2d 583 the United States Supreme Court stated the test for a constitutional instruction on reasonable doubt: "... so long as the court instructs the jury on the necessity that the defendant's guilt be proven beyond a reasonable doubt, the constitution does not require any particular form of words to be used in advising the jury of the government's burden of proof. Rather, taken as a whole, the instructions must correctly convey the concept of reasonable doubt to the jury." (Id., at p. 5, 114 S.Ct. at p. 1242; internal citations and quotation marks omitted.)