Create two urls (easier to create two cms items. Post-1 and post-1-v2 - and maybe use if to change content). Than by google optimize create split test:
A redirect test, (a.k.a. split URL test) , is a type of A/B test that allows you to test separate web pages against each other
Since Google Optimize has sunsetted, and if anyone is still looking for a way of doing it…
Mida.so can do that with URL redirection with wildcard matching. For example, you want to split traffic between site .com/collection-a/page and site .com/collection-b/page
You just create a split URL redirection rule with wildcards:
Control: site .com/collection-a/*
Variant 1: site .com/collection-b/*