turn the light on and leave it on for about an hour, go back to it, and put your hand near it, feel the heat, if it's really hot and you're not even touching it, then it's useless

i would just try to grow some other types of plants under it, maybe a tomato and just some flowers, let them sit under the light for a while just to see how they do...you'll see within the first week prolly if they're taking to it well