Details: Failed invoking <symbol>

Hello,

In a WatchUi.BehaviorDelegate class, in the onMenu() function, I'm trying to call a function from another class (the read() function from the Test class), but the application crashes.

Error code:

Error: Unexpected Type Error
Details: Failed invoking <symbol>
Stack: 
  - onMenu() at C:\Users\bapti\OneDrive\Bureau\ble\source\viewDelegate.mc:34 0x100000f1 
  - handleEvent() at 704b03c0.mb:1462 0x30002969 

Encountered app crash.

Code :

import Toybox.Lang;
import Toybox.WatchUi;
import Toybox.BluetoothLowEnergy;

class viewDelegate extends WatchUi.BehaviorDelegate {
    
    var test as Test?;

    public function initialize() {
        BehaviorDelegate.initialize();
        test = _test; //new $.Test();
    }


    function onMenu() as Boolean {
        test.read();
        //WatchUi.pushView(new Rez.Menus.MainMenu(), new bleMenuDelegate(), WatchUi.SLIDE_UP);
        return true;
    }


}

import Toybox.Graphics;
import Toybox.WatchUi;
import Toybox.BluetoothLowEnergy;
import Toybox.Lang;


class Test {
    function initialize() {        
    }

    function read(){
    }
}

Can you help me ?