the reason why moving in to test out whether to get married is such a bad idea is that the whole premise goes against what a big portion of marriage is about.
moving in together is about "well is something starts bothering in a few years i can always opt out" where as in marriage "if something starts bothering me in a few years , atleast i have some one i fully trust to work this out no matter how hard it may be."
to be serious, live in is jsut for sex and economical convenience , dont dissolusion yourself thinking its about love.
here a quick
LINK
i found, there are many many more studies on the effects of live in couples.
over all taking two couples who are both having a long term relation ship, the couple not living in together is a) mor likely to get married b) have a more stable relationship c) less likely to get a divorce