Although any light source other than real sunlight is a compromise, the repeatability of artificial light sources makes them a good compromise, if your tests don't need to result in laboratory grade accuracy. For example, my purposes I would be happy to be within 1/3 stop accuracy, 2/3 stop is tolerable. Once I get into the field to take pictures, I can't get my light meter readings to within 1/3 stop accuracy/repeatability anyway.