What is the test for a plaintiff to claim damages for loss of enjoyment of life as a result of injury?

I adopt, as did Esson J., the following passage from Tzouvelis v. Victorian Ry. Commr., [1968] V.R. 112 at 135-36, as correctly stating the applicable law: It has in recent years been repeatedly laid down that, when the plaintiff in a negligence action establishes that, by reason of his injuries his ability to earn wages had been destroyed or impaired, the loss in respect of which he is entitled to be compensated is not a future loss of earnings, but the present destruction or impairment of a capacity or faculty: … The destruction or impairment of the capacity or faculty has, of course, two aspects. The plaintiff thereby loses satisfactions and suffers frustrations, and these matters are ordinarily taken into account under the general head of loss of enjoyment of life. In addition the plaintiff suffers an economic loss because the capacity or faculty destroyed or impaired is a thing of economic value to him. Since such a capacity cannot, of course, be sold outright, its economic value, like that of tangible property which cannot be sold, needs to be assessed by reference to the present value of the future economic benefits which it would have produced. It is not, in my view, a matter of what it could have produced, but of what it would, in fact, have produced.