An apparatus and method is described for testing a multi-hole fuel injector nozzle. The apparatus comprises mounting means for the multi-hole nozzle and fuel supply means for supplying fuel to the multi-hole nozzle. The multi-hole nozzle is mounted outside a measurement chamber for capturing the fuel spray from an individual spray hole outlet of the multi-hole nozzle. In one embodiment, the apparatus includes a spray target plate, located within the measurement chamber, at which the fuel spray is directed. The spray target plate (28) is connected to a remote pressure sensor, which is used to determine the spray force of the fuel spray acting on the spray target plate. The apparatus is further arranged to determine the mass flow rate of the fuel spray. A new parameter, referred to as ‘momentum efficiency’ is defined, and calculated using the determined values of spray force and mass flow rate.