What is the test for establishing that a defendant has committed uncharged criminal acts that are similar to the charged offense?

"[E]vidence that the defendant has committed uncharged criminal acts that are similar to the charged offense may be relevant if these acts demonstrate circumstantially that the defendant committed the charged offense pursuant to the same design or plan he or she used in committing the uncharged acts. Unlike evidence of uncharged acts used to prove identity, the plan need not be unusual or distinctive; it need only exist to support the inference that the defendant employed that plan in committing the charged offense." (People v. Ewoldt (1994) 7 Cal.4th 380, 403.)