An apparatus for in vitro testing of medical device thrombogenicity includes an enclosure; a heating element thermally coupled to the enclosure; and a temperature feedback circuit operably coupled to the heating element and configured to control the heating element to maintain an interior of the enclosure within a preset temperature range. Positive, negative, and intermediate control rods are provided as standards against which to compare a medical device test article. Multiple blood test loops can be established through the enclosure using a common blood supply. The medical device test article can be placed in one of the loops, while the remaining loops can contain controls. Blood can be circulated through the test loops at a flow rate similar to that encountered in vivo, and thrombus formation can be assessed thereafter.