What is the test for a motion to strike a cause of action against a person in furtherance of their right of petition or free speech?

Code of Civil Procedure section 425.16, subdivision (b)(1) provides that a "cause of action against a person arising from any act of that person in furtherance of the person's right of petition or free speech under the United States or California Constitution in connection with a public issue shall be subject to a special motion to strike, unless the court determines that the plaintiff has established that there is a probability that the plaintiff will prevail on the claim." "[T]he statutory phrase 'cause of action . . . arising from' means simply that the defendant's act underlying the plaintiff's cause of action must itself have been an act in furtherance of the right of petition or free speech. [Citation.] In the anti-SLAPP context, the critical point is whether the plaintiff's cause of action itself was based on an act in furtherance of the defendant's right of petition or free speech. [Citations.]" (City of Cotati v. Cashman (2002) 29 Cal.4th 69, 78.)