What is the test for inducing breach of contract?

I agree with and adopt the statement of the law as is contained in the text The Law of Damages, Waddams, Canada Law Book Limited, 1983. One finds the following statement at p. 321, paras. 561-562: "Several kinds of action may lie against one who induces another to break a contract with the plaintiff. These include the tort of inducing breach of contract, conspiracy, in timidation, and causing harm by wrongful means. The gist of the plaintiff's complaint is that he has been deprived of the benefit of a contract and the prima facie measure of damages will be the amount that could have been recovered in a judgment against the contracting party for breach of contract. A primary reason for the development of the action against the person induc ing breach was that the contracting party might be unable to pay: 'The servant or contractor may be utterly unable to pay anything unlike the amount of the damage sustained en tirely from the wrongful act of the defendant; and it would seem unjust, and contrary to the general prin ciples of law, if such wrongdoer were not responsible for the damage caused by his wrongful and malicious act.' "However, the plaintiff is not en titled to recover damages twice over for the same loss and it was accepted in Jones v. Fabbi that judgment could be given against both the contract breaker and the inducer on the understanding that satisfaction of the judgment by the inducer would reduce the liability of the contract breaker." (The citation for Jones v. Fabbi is (1973), 37 D.L.R.(3d) 27, a decision of the British Columbia Supreme Court.)