What is the test for damages when a contract is breached?

We must also remember the fundamental rule laid down in Hadley v. Baxendale that the measure of damages is the amount of loss that was reasonably contemplated by the parties at the time of making the contract as being the probable result of breach. In other words, damages are measured according by those consequences of breach which the parties as reasonable people would, if they had thought about it, have foreseen and accepted as natural and probable: Biggin v. Permanite, [1951] 1 K.B. 422 at 433, per Devlin J.