What is the legal test for establishing that the testator knew and approved the contents of a will?

Where suspicious circumstances exist, however, the rebuttable presumption that the testator knew and approved of the contents of the will no longer applies. In such circumstances, the propounder of the will assumes the legal burden of proving knowledge and approval. If the suspicious circumstances relate to mental capacity, the propounder of the will also assumes the legal burden of establishing testamentary capacity: Vout v. Hay, 1995 CanLII 105 (SCC), [1995] 2 S.C.R. 876, at paras. 25-27.