Test is Tom Bruno on drums; Daniel Carter, woodwinds and piano; Sabir Mateen, woodwinds and piano; Matthew Heyner on bass.
From a chapter from New York Is Now! The New Wave of Free Jazz, by Phil Freeman (2001):
Test, if such a profoundly collective ensemble can be labeled one man’s idea, was the inspiration of its drummer, Tom Bruno. Bruno was performing solo, and doing occasional duos with other musicians, in the subways as part of the City’s Music Under New York program. Musicians who participate in the program are assigned locations by the MUNY administrators, and are provided with subway tokens and occasional help finding other bookings. “I was in the program,” Bruno told me, “and Daniel Carter was doing solo stuff. I saw him in the office, and thought I wanted to work with him. So after a trip I took to Berlin, I contacted him and we formed a trio with a bassist, Dan O’Brien.” This group played together for a short time, but O’Brien soon departed. Enter new bassist Matt Heyner, and saxophonist Sabir Mateen. The lineup hasn’t changed since.