What is the test for making a conspiracy determination based on two phone calls between 2 phone calls?

Respondent also argues that People v. Jeffery (1995) 37 Cal.App.4th 209, 215, allows the conspiracy determination to be made in the context, and with the benefit, of reference to later events. Respondent then argues that appellant's fortuitous appearance as the wheelman in a convenience store drug sale that occurred within minutes of the two phone calls weighs heavily in favor of finding that the conspiracy existed at the time of those phone calls.