The Quartet high-performance downhole reservoir testing system delivers high-quality pressure measurements and fluid samples with increased safety and efficiency for better reservoir testing. The system integrates four testing technologies into one string to allow the operator to isolate, control, measure, and sample in a single run. The downhole test string offers benefits over conventional test strings, including a shorter string design, lower operating pressure, less nitrogen, and fewer seals and connections. In addition, drill collars and slip joints are eliminated from the string.