Don't waste your money!!
I had two, one by York test laboratories. They told me I was allergic to loads of foods based on a blood test. After trying the diet for a long time, I eventually found that those foods gave me no problems whatsoever. I eat them all happily now, they don't correlate with my symptoms at all.
Also the nutritionist with whom I had phone call sessions that they provided knew absolutely nothing. He told me I had "leaky gut syndrome" and that I would heal and feel better by following his dietary advice for a few months. At the end of the months during which I followed his advice to the letter, my digestive symptoms were worse than any other time in my life, before or since. I kept telling the nutritionist that my weight kept dropping and I couldn't eat enough to keep a healthy weight on this diet, but he told me to keep with it anyway, and that he didn't understand why I couldn't gain weight.
I had a second test by a nutritionist who had a "vega" machine. It said I was allergic/intolerant to a completely different set of foods that the York test. Again, following her advice I lost weight I didn't need to lose, and my symptoms got worse, not better. She actually got angry with me when I told her I wasn't feeling better, said I must be cheating and sneaking bars of chocolate or something (I wasn't) and stopped returning my calls.
The reason I got worse on their diets, I have since learned, was because they had me eating lots of fruit and veg and nuts and seed, and I can't handle too much fibre. And the reason their food intolerance tests didn't work was because they are completely meaningless tests.
Your doctor can test you for lactose intolerance, and you can be tested for coeliac (allergy to gluten). Apart from that, I don't think you can be intolerant to foods, and if you had a true allergy, you'd know it immediately because you'd have a severe reaction to the food. Some foods may give you more problems than others, but the only way to find out which foods hurt you, is to find out by trial and error - there's no test. Some foods are known to give many problems, so trying without the most common difficult foods - like those high in fibre, dairy, wheat, etc. may be good ones to test yourself for first.