fix: Add EmptyClusterStrategy for test mode

apps/core/test/support/empty_cluster_strategy.ex

@@ -0,0 +1,24 @@
+defmodule Legendary.Core.Cluster.EmptyClusterStrategy do
+  @moduledoc """
+  A libcluster nil strategy that always returns no nodes.
+  """
+  use GenServer
+  use Cluster.Strategy
+
+  alias Cluster.Strategy.State
+
+  def start_link([%State{} = state]) do
+    new_state = %State{state | :meta => []}
+    GenServer.start_link(__MODULE__, [new_state])
+  end
+
+  @impl true
+  def init([state]) do
+    {:ok, state, :infinity}
+  end
+
+  @impl true
+  def handle_info(_, state) do
+    {:noreply, state, :infinity}
+  end
+end

config/test.exs

@@ -41,3 +41,10 @@ config :core, Legendary.CoreMailer, adapter: Bamboo.TestAdapter
 config :content, Oban, crontab: false, queues: false, plugins: false
 
 config :logger, level: :warn
+
+config :libcluster,
+  topologies: [
+    erlang_hosts: [
+      strategy: Legendary.Core.Cluster.EmptyClusterStrategy
+    ]
+  ]