How iRule works when a persistence adapted?

You maybe have some conflicting logic here. At the very least I'd suggest inserting some logging to see how things are really being handled.

when HTTP_REQUEST {
    if { [HTTP::header exists "X-True-IP"] } {
        set clientip [HTTP::header "X-True-IP"]
    } else {
        set clientip [IP::client_addr]
    }
    set uri [string tolower [HTTP::uri]]
    if { $uri contains "/test.xml" } then {
        if { ( [class match $clientip equals CCclient] ) } then {
            log local0. "uri contains /text.xml - sending to pool B"
            pool B
        } else {
            log local0. "sending 404 response"
            HTTP::respond 404 content "404 File Not Found"
        }
    }
    if { $uri contains "ref=trust" } {
        log local0. "uri contains ref=trust - sending to pool B"
        pool B
    } else {
        log local0. uri doesn't contain ref=trust - sending to pool A"
        pool A
    }
}

So basically, for it to go to pool B, the request URI has to contain "/test.xml" AND "ref=trust", and the IP has to be in the data group.