How much evidence must be taken to prove the amount of damages in an action for breach of contract?

[266 Cal.App.2d 583] Evidence must be taken to prove the amount of damages in an action sounding in tort (Taliaferro v. Hoogs, 219 Cal.App.2d 559, 560, 33 Cal.Rptr. 415); likewise in an action to recover under a contract where the complaint seeks to recover an amount other than a specified amount set forth in the contract itself, or for breach of a contract that does not express the amount of liquidated damages. (Lynch v. Bencini, 17 Cal.2d 521, 526--527, 110 P.2d 662.)