Abstract: An apparatus for in situ borehole testing having a drill string with drill pipe and drill bit. An upper sleeve and lower sleeve are telescopically coupled together. A valve seat is located in an interior passage and closes the interior passage when a valve member is seated in the valve seat. A plurality of separate inflatable packers are coupled to the lower sleeve and activated when the valve member is seated in the valve seat. A latching collet having teeth positively interlocks with spline teeth affixed to the inner wall of the upper sleeve. A hydraulic valve assembly is attached to the lower sleeve and is activated by fluid in one of a plurality of separate fluid chambers which communicate with and inflate the separate packers.