What is the test for establishing that a testator in a will had knowledge and approval of the contents?

In Vout v. Hay, 1995 CanLII 105 (SCC), [1995] 2 S.C.R. 876 Sopinka, J. stated, at paras. 27 and 28 of his judgment: …Upon proof that the will was duly executed with the requisite formalities, after having been read over to or by a testator who appeared to understand it, it will generally be presumed that the testator knew and approved of the contents and had the necessary testamentary capacity. Where suspicious circumstances are present, then the presumption is spent and the propounder of the will reassumes the legal burden of proving knowledge and approval. In addition, if the suspicious circumstances relate to mental capacity, the propounder of the will reassumes the legal burden of establishing testamentary capacity. Both of these issues must be proved in accordance with the civil standard. A1. Requisite formalities