Exactly, that's why we searched for a package. In the end we created our own you can find here: https://github.com/bart/ab
We are not able to use providers like Optimizely and Google A/B because we don't just want to change one button but instead about 70% of the page including logical stuff (which needs changes in our core Vue components). For sure, there maybe is some way to handle it with those tools but in the end in my opinion this will take more effort than coding it into the project itself. For us this was the best solution.