title: How to test for MessageAdapter Effect with BehaviorTestKit
body: <p>I'm trying to use <code>BehaviorTestKit</code> to test my behavior and the creation of the behavior invokes</p>
  
  <pre><code>val ackMapper: ActorRef[Ack] = context.messageAdapter(x =&gt; EventAck(x.id))
  </code></pre>
  
  <p>which results in a <code>MessageAdapterEffect</code>. However, I cannot seem to find a way to create a <code>MessageAdapterEffect</code> that will satisfy <code>expectEffect</code></p>
  
  <pre><code>testKit.expectEffect(MessageAdapter[Ack, EventAck](classOf[Ack], ack =&gt; EventAck(ack.id)))
  </code></pre>
  
  <p>results in a type mismatch because the lambda, while functionally equivalent, is a different instance. Neither can I access the lambda created inside the behavior since it is hidden inside the closure of creating the behavior.</p>
  
  <p>How is <code>expectEffect</code> meant to work for <code>MessageAdapter</code>?</p>