What is the test for establishing that the Fly Boys were a criminal street gang?

In this case, the prosecution proceeded on the theory that the Fly Boys were a criminal street gang. Appellants contend there is insufficient evidence that the gang even existed. To establish that a gang is a "criminal street gang" within the meaning of the gang enhancement statute, the prosecution must prove, among other elements, that the gang is an "ongoing organization, association, or group of three or more persons, whether formal or informal, ... having a common name or common identifying sign or symbol ...." ( 186.22, subd. (f).) While a "formal group" may often reflect well-defined membership criteria, a discernible hierarchy, predictable meeting schedules and locations, fixed membership groups, and codified rules and order, an "informal group" will rarely if ever display these characteristics. (People v. Prunty (2015) 62 Cal.4th 59, 73 (Prunty).) An informal group "need not exhibit an identifiable hierarchy; their membership composition may be fluid; their boundaries of the their 'turf' may be porous; and their methods of communication may be variable." (Ibid.) However, an "organization, association, or group" must be more than "three or more persons, ... having a common name or common identifying sign or symbol," and there must be "a degree of physical togetherness or the engagement in common activities ...." (Id. at p. 75.)