What is the test for establishing knowledge and approval of a will?

[17] Sopinka J. in Vout v. Hay, supra at paras. 26, 27, 28 and 29 stated the law as follows: ...Although the propounder of the will has the legal burden with respect to due execution, knowledge and approval, and testamentary capacity, the propounder is aided by a rebuttal presumption. 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. There is nothing mysterious about the role of suspicious circumstances in this respect. The presumption simply casts an evidentiary burden on those attacking the will. This burden can be satisfied by adducing or pointing to some evidence which, if accepted, would tend to negative knowledge and approval or testamentary capacity. In this event, the legal burden reverts to the propounder. ...To disallow probate by reason of circumstances merely raising a suspicion of fraud or undue influence would tend to defeat the wishes of the Testator in many cases where in fact no fraud or undue influence existed, but the propounder simply failed to discharge the legal burden. Accordingly, it has been authoritatively established that suspicious circumstances, even though they may raise a suspicion concerning the presence of fraud or undue influence, do no more than rebut the presumption to which I have referred. This requires the propounder of the will to prove knowledge and approval and testamentary capacity. The burden of proof with respect to fraud and undue influence remains with those attacking the will. “...Undue influence, in order to render a will void, must be an influence which can justly be described by a person looking at the matter judicially to have caused the execution of a paper pretending to express a Testator’s mind, but which really does not express his mind, but something else which he did not really mean.”.... A person may well appreciate what he or she is doing but be doing it as a result of coercion or fraud.