mortgage stress tests for homebuyers with uninsured mortgages starting June 1.The minimum qualifying rate for uninsured mortgages – residential mortgages with a down payment of 20 per cent or more – will rise to either the contracted rate plus two percentage points or 5.25 per cent, whichever is higher.As it stands, any buyer whose down payment on a home is one-fifth of the purchase price or more has to show they can afford mortgage payments if the interest rate was two percentage points higher than what the bank is offering them or the five-year benchmark rate published by the Bank of Canada, which sits at 4.79 per cent — whichever is higher.