`Helpers.testServerPort` would be better here, but the best thing is to do:

```scala
class NettyServerThreadNamingSpec extends PlaySpecification with WsTestCient 
```

And then your test can be as simple as this:

```scala
in new WithServer(FakeApplication(withRoutes = {
  case _ =>
   val threadName = Thread.currentThread.getName
   Action(Ok(threadName))
})) {
  (await(wsCall("/").body)) must beMatching("play-netty-worker-\\d$")
}
```