While I agree with this and do it in my own life, I don't think that taking a trip is enough to ensure a relationship is a success.
As an example: my partner and I have been on several trips to other continents. We've managed to make it through these trips without breaking up, and while having a reasonably fun time.
But while trips are stressful and are the ultimate test of your ability to compromise/communicate, it isn't the same as daily life together.
For example, my partner loves to leave dirty dishes in the sink to wash later. I prefer to do the dishes immediately so when I come by later to use the sink, it's not full of dirty dishes. It's small, but persistently annoying. We're both working on our tolerance for dirty dishes. (Before someone suggests buying a dish washer, our European apartment is too small for one, so the sink is the only option).
This not the kind of thing you'd notice on vacation.
As such, they offer a poor window through which to preview the feasibility of everyday domestic life.
For example: When putting together furniture, do you like to read the instructions, or just dive right in?
It is important to do at least some projects together, and take some trips where you face at least a little adversity to get a good measure of how well you two can work together.
Doing that can also help you find other potential problem areas, like differences in communication style. You will inevitably have conflict, the question is how will you work things out.