The Court of Appeal decision of LeVan v. LeVan, sets out a two part test for determining whether a domestic contract should be set aside under s. 56(4) of the FLA:
1) the court must consider whether the party seeking to set aside the agreement can demonstrate that one or more of the circumstances set out within the provision have been engaged.
2) the court must then consider whether it is appropriate to exercise discretion in favour of setting aside the agreement.
http://www.canlii.org/en/on/onca/doc/2008/2008onca388/2008onca388.html