Hello,

I’m trying to test channels in a cluster of nodes using local-cluster.

Though it does not work when joining channel from the created nodes.

It fails with: socket/1-3 can only be invoked from the test process

Originally I had first seen that issue when testing channels outside of test process

phoenixframework/phoenix#5326

Using test_process: pid would solve it, though when used within Node.spawn, it does not

Here is a piece of code that reproduces the issue

setup_all do
    {:ok, cluster} =
      LocalCluster.start_link(3,
        files: [
          __ENV__.file
        ]
      )

    {:ok, nodes} = LocalCluster.nodes(cluster)

    on_exit(fn ->
      LocalCluster.stop(cluster)
    end)

    [nodes: nodes]
  end

def newClient(userPK, topic, pid) do
    socket =
      MessagesWeb.UserSocket
      |> socket("", %{user_id: userPK}, test_process: pid)
      |> subscribe_and_join(
        MessagesWeb.Room,
        "rooms:#{topic}"
      )
  end

 test "join channels in cluster", %{nodes: [node1, node2, node3]} do
 pid = self()
 users = 10000
 {_n1_pid, ref} =
      Node.spawn(node1, fn ->
          map =
          Enum.map(
            1..users,
            fn pk ->
              Task.async(fn ->
                socket = newClient(pk, "sf6", pid)
                :timer.sleep(:timer.minutes(15))
              end)
            end
          )
      end)
end