I can't speak to any tests or studies, but I can tell you that my brother healed his candida using Duncan Crow's Whey/Inulin/Selenium Protocol. He took Whey/Inulin/Selenium for a couple months, then hit the yogurt and buttermilk really hard for a couple of months.
Before this, he was unable to concentrate, had to eat every 2 hours, had major anxiety, etc. After, he gets zero food reactions, has tons of energy, is able to drive cross country (before he had trouble driving across town due to anxiety/trouble concentrating).
I've not had as much success with Duncan Crow's Protocol, but I took antibiotics for 4 years, whereas my brother took them for a shorter amount of time. Personally, I am finding great results with the McCombs Plan - when I stick to it! I do find value in prebiotics too, however. I had chronic diarrhea for years and Inulin cleared that up in 2 days!