What is the test for establishing an agreement?

"To prove an agreement, it is not necessary to establish the parties met and expressly agreed [to commit the target offense]." People v. Vu, 143 Cal. App. 4th 1009, 1025 (2006). "The evidence is sufficient if it supports an inference that the parties positively or tacitly came to a mutual understanding to commit a crime." People v. Prevost, 60 Cal. App. 4th 1382, 1399 (1998). The existence of a conspiracy "may be proved through circumstantial evidence inferred from the conduct, relationship, interests, and activities of the alleged conspirators before and during the alleged conspiracy." Id.