Hi, I created some Unit test to test my GenServer which handles Mnesia in its state, and I need to run some function before each test like delete Mnesia Data on my disk, but I get error like this in each function or GenServer call back which has Mnesia function on it self

Error:

     ** (exit) exited in: GenServer.call(MishkaDatabase.Cache.MnesiaToken, {:get_token_by_user_id, "61095b8c-b172-42c6-8759-b64cacaee32d"}, 5000)
         ** (EXIT) normal

The test I used:

  def delete_old_tokens(_context) do
    MnesiaToken.delete_all_tokens() # this is `handle_cast`
  end

  setup :delete_old_tokens

  test "Get code with code" do
      %{} = assert MnesiaToken.get_token_by_user_id(Ecto.UUID.generate)
  end

now this is my GenServer code:

  def get_token_by_user_id(user_id) do
    GenServer.call(__MODULE__, {:get_token_by_user_id, user_id}, @timeout)
  end
  @impl true
  def handle_call({:get_token_by_user_id, user_id}, _from, state) do
    token_selected = Mnesia.transaction(fn ->
      Mnesia.select(Token, [{{Token, :"$1", :"$2", :"$3", :"$4", :"$5", :"$6"}, [{:"==", :"$2", "#{user_id}"}], [:"$$"]}])
    end)
    |> case do
      {:atomic, []} -> %{}
      {:atomic, data} -> data
      _ -> %{}
    end

    {:reply, token_selected, state}
  end

and my def to delete all Mnesia data before each test

  def delete_all_tokens() do
    GenServer.cast(__MODULE__, {:delete_all_tokens})
  end

  @impl true
  def handle_cast({:delete_all_tokens}, state) do
    Mnesia.transaction(fn ->
      Mnesia.select(Token, [{{Token, :"$1", :"$2", :"$3", :"$4", :"$5", :"$6"}, [], [:"$$"]}])
    end)
    |> case do
      {:atomic, []} -> {:noreply, state}
      {:atomic, data} ->
        Enum.map(data, fn [id, _user_id, _token, _access_expires_in, _create_time, _os] ->
          Mnesia.dirty_delete(Token, id)
        end)
        {:noreply, state}
      _ -> {:noreply, state}
    end
  end

I think this problem is started when the GenServer cant stay to get answer then I use big timeout, unfortunately this didn’t help me.

more problem

I cant create a loop before each test to check whether we have data on mnesia disk or not. it shows me same error like top, for example create check all the token on disk

  def get_all_token() do
    GenServer.call(__MODULE__, {:get_all_token})
  end
  def handle_call({:get_all_token}, _from, state) do
    Mnesia.transaction(fn ->
      Mnesia.select(Token, [{{Token, :"$1", :"$2", :"$3", :"$4", :"$5", :"$6"}, [], [:"$$"]}])
    end)
    |> case do
      {:atomic, []} -> {:reply, %{}, state}
      {:atomic, data} -> {:reply, data, state}
      _ -> {:reply, %{}, state}
    end
  end

again we have a Mnesia checker into GenServer call back and it doesn’t want to answer us

it should be noted I don’t want to save a copy of disk mnesia on my GenServer state

Please help me to create some test for this
Thanks