Not so long ago when I used to work for an industrial company who was the global leader in dressings, we used to test our mayonnaise alongside competitors as well as our other brands from other countries. You see, each country in Asia has their own definition of mayonnaise legally and it's usually defined by the oil content. Let's just say that The Philippines requires more oil content than Singapore, so you know which one to buy depending on your dietary requirements. Of course, taste also differs, so be mindful of these changes!
Whenever we would benchmark, we always used the same recipe with the same proportions so that we always end up tasting and seeing significant changes. We also always chose a neutral carrier like a potato. It also helps when the recipe is fairly easy to prepare so that tests can be rolled-out in less than an hour. I always chose the humble Potato Salad.
Boil some water, season it with salt, and cook the potatoes until soft. Add mayonnaise and garnish with scallions and chives. However, it is good to note that for tests, we don't season the water with salt and we don't garnish with scallions and chives -- we keep it to a minimum of just potatoes and mayonnaise! And oh, chill before serving.