What is the legal test for determining pre-judgment interest?

Unless the provisions regarding interest rates are vague or unclear, or unless the interest rate infringes a statutory provision such as the Interest Act, effect should be given to the contractual rate for the determination of both pre- and post-judgment interest: Capital One Bank v. Matovska, [2007] O.J. No. 3368 (Div. Ct.). In this case, the rate provided for in the contract is neither unclear nor illegal.