Is the legal test for capacity to marry different from the test for capacity to make a will in Ontario?

Yes, they're legally distinct tests, even though both matter in predatory marriage and estate planning disputes. Testamentary capacity focuses specifically on whether the person understood the nature of making a will, generally knew the extent of their property, and understood who might reasonably expect to benefit from their estate, assessed at the time the will was signed. Capacity to marry is a different, generally more basic legal question, focused on whether the person understood the nature of the marriage relationship itself and the responsibilities that come with it.

Because the tests are different, it doesn't automatically follow that someone found to lack testamentary capacity also lacked capacity to marry, or that someone capable of marrying was necessarily capable of making a valid will — each needs to be assessed separately, on its own evidence, at the relevant time. This distinction is especially important in predatory marriage situations, where a person might be found capable of understanding a simple marriage relationship while genuinely lacking the more complex understanding needed to manage property or make informed decisions about a will. Anyone dealing with a situation involving both a suspect marriage and a will should get legal advice on how each test applies separately to their facts.