What is the test for whether an offer was an offer that ought reasonably to have been accepted?

With respect to whether it was an offer that ought reasonably to have been accepted, the often-cited decision in Hartshorne v. Hartshorne, 2011 BCCA 29, contains some helpful comments:

The first factor – whether the offer to settle was one that ought reasonably to have been accepted – is not determined by reference to the award that was ultimately made. Rather, in considering that factor, the court must determine whether, at the time that the offer was open for acceptance, it would have been reasonable for it to have been accepted: Bailey v. Jang, 2008 BCSC 1372, 90 B.C.L.R. (4th) 125 at para. 24; A.E. v. D.W.J. at para. 55. As was said in A.E. v. D.W.J., “The reasonableness of the plaintiff’s decision not to accept the offer to settle must be assessed without reference to the court’s decision” (para. 55). Instead, the reasonableness is to be assessed by considering such factors as the timing of the offer, whether it had some relationship to the claim (as opposed to simply being a “nuisance offer”), whether it could be easily evaluated, and whether some rationale for the offer was provided. We do not intend this to be a comprehensive list, nor do we suggest that each of these factors will necessarily be relevant in a given case.