What is the legal test for obtaining permission to amend a motion to dismiss?

To obtain the court's permission, plaintiffs were required to file a noticed motion for leave. (Id. at p. 613.) A court can deny a motion to dismiss and allow the plaintiff to file an amended complaint, provided plaintiff gives an excuse for the delay. (Contreras v. Blue Cross of California (1988) 199 Cal.App.3d 945, 948.) "'The law is well settled that a long deferred presentation of the proposed amendment without a showing of excuse for the delay is itself a significant factor to uphold the trial court's denial of the amendment. [Citation.] [Citation.]'" (Leader, supra, at p. 613.) This is true even if the plaintiff proposes a good amendment in proper form. (Ibid.)