What is the test for materiality of a misrepresentation?

The leading cases on materiality refer to Fleming v. Boultbee, [1929] O.W.N. 293, where it was set out at p. 296: A misrepresentation goes for nothing unless it is a proximate and immediate cause of the transaction. It is not enough that it may have remotely or indirectly contributed to the transaction and may have supplied a motive to the other party to enter into it. The representation must be the very ground on which the transaction has taken place. The transaction must be a necessary and not merely an indirect result of the representation. It is not, however, necessary that the representation should have been the sole cause of the transaction. It is enough that it may have constituted a material inducement.