What is the test for a plaintiff to succeed in a claim of retaliation against a defendant for filing a grievance?

First, the plaintiff must allege that the retaliated-against conduct is protected. The filing of an inmate grievance is protected conduct. Rhodes v. Robinson, 408 F.3d 559, 568 (9th Cir. 2005). A prisoner's formal and informal grievances, whether in writing or verbal, are protected conduct under First Amendment. Entler v. Gregoire, 872 F.3d 1031 (9th Cir. 2017)

Second, the plaintiff must claim the defendant took adverse action against the plaintiff. Rhodes, 408 F.3d at 567. The adverse action need not be an independent constitutional violation. Pratt v. Rowland, 65 F.3d 802, 806 (9th Cir. 1995). [T]he mere threat of harm can be an adverse action.... Brodheim, 584 F.3d at 1270.

Third, the plaintiff must allege a causal connection between the adverse action and the protected conduct. Because direct evidence of retaliatory intent rarely can be pleaded in a complaint, allegations of a chronology of events from which retaliation can be inferred is sufficient to survive dismissal. See Pratt, 65 F.3d at 808 (timing can properly be considered as circumstantial evidence of retaliatory intent); Murphy v. Lane, 833 F.2d 106, 108-09 (7th Cir. 1987).