What is the test for establishing that a will was executed properly?

The court goes on to quote from Vout v. Hay, 1995 CanLII 105 (SCC), [1995] 2 S.C.R. 876, para 26: 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.

The court in Vout v. Hay then states that the presumption can be rebutted if there are suspicious circumstances surrounding the preparation of the will, or circumstances that call into question testamentary capacity or whether the free will of the testator was overborne by acts of coercion or fraud. The legal burden then reverts to the propounder of the will.