F5 irule: HTTP_REQUEST switch -glob HTTP::uri not working with pool

Perhaps I don't understand what you mean. On the Virtual Server, you assign a default pool. Let's call that pool-default. Naturally, without an iRule, you should see traffic forwarded to members of that pool. When you apply the iRule, you say "it does not load". What do you mean by that? Do you mean it does not forward the traffic to any pool member? What happens when you simply set the pool on the Virtual Server to test_pool? Does it load balance traffic to members of that pool?

If it does not, are any of the pool members marked as "up" by the pool (or node-specific) monitor(s)?

If pool members are up, but traffic forwarding does not appear to be happening, do the pool members of test_pool have the BIG-IP in their default route path? If not, are you using SNAT on the Virtual Server?