What is the test for enforceability of a forum selection clause in a commercial contract?

As the Court of Appeal said in Expedition Helicopters v. Honeywell Inc. [15] A forum selection clause in a commercial contract should be given effect. The factors that may justify departure from that general principle are few. The few factors that might be considered include the plaintiff was induced to agree to the clause by fraud or improper inducement or the contract is otherwise unenforceable, the court in the selected forum does not accept jurisdiction or otherwise is unable to deal with the claim, the claim or the circumstances that have arisen are outside of what was reasonably contemplated by the parties when they agreed to the clause, the plaintiff can no longer expect a fair trial in the selected forum due to subsequent events that could not have been reasonably anticipated, or enforcing the clause in the particular case would frustrate some clear public policy. Apart from circumstances such as these, a forum selection clause in a commercial contract should be enforced.