Codeception Test - Inconsistent Result with yii2 events

Yii 2.0 Testing
1

I am testing a simple event as follows …

I have an event class to pass data

class EventMakeCurrent extends Event {
	public bool $result=false;
}

A sender model to populate the event data raise the event

class SenderModel extends Model {
	public function triggerEvent() : EventMakeCurrent{
		$e = new EventMakeCurrent();
		Event::trigger(SenderModel::class, 'event', $e);
		return $e;
	}
}

And a receiver class with a class level event handler to process the event

Event::on(SenderModel::class, 'event', function($e){
  $e->result = true;
  $e->note = date('h:i:s', time());
  return;
});
class ReceiverModel extends Model
{

}

My unit test is as follows…

class EventTestTest extends Unit
{
	public function testEventTrigger()
	{
		$sender = new SenderModel();
		$receiver = new ReceiverModel();
		$resultEvent = $sender->triggerEvent();
		$this->assertTrue($resultEvent->result);
	}

	public function testSecondEventTrigger()
	{
		$sender = new SenderModel();
		$receiver = new ReceiverModel();
		$resultEvent = $sender->triggerEvent();
		$this->assertTrue($resultEvent->result);
	}
}

Edit:
The following test passes.

public function testEventTrigger()
	{
	$sender = new SenderModel();
	$receiver = new ReceiverModel();
	$resultEvent = $sender->triggerEvent();
	$this->assertTrue($resultEvent->result);

	$sender = new SenderModel();
	$receiver = new ReceiverModel();
	$resultEvent = $sender->triggerEvent();
	$this->assertTrue($resultEvent->result);
}

The first test passes, then the next identical test fails.
The events is not raised or received in the second test ?

Edit… It seems in the second test that the Event object does not have my event registered.
Returns at.

        if (empty(self::$_events[$name]) && empty($wildcardEventHandlers)) {
            return;
        }

Can anyone reproduce?
Thanks