@Test
public void retrieveMetricsInClosedStateDoesNotStartClientActor() {

    new TestKit(actorSystem) {{
        final TestProbe probe = TestProbe.apply(actorSystem);
        final ActorRef underTest =
                TestConstants.createConnectionSupervisorActor(connectionId, actorSystem, pubSubMediator,
                        proxyActor,
                        (connection, concierge, connectionActor) -> MockClientActor.props(probe.ref()));
        watch(underTest);
        // create connection
        underTest.tell(createClosedConnection, getRef());
        expectMsg(createClosedConnectionResponse);
        probe.expectNoMessage();
        // retrieve metrics
        underTest.tell(RetrieveConnectionMetrics.of(connectionId, DittoHeaders.empty()), getRef());
        probe.expectNoMessage();
        final RetrieveConnectionMetricsResponse metricsResponse =
                RetrieveConnectionMetricsResponse.getBuilder(connectionId, DittoHeaders.empty())
                        .connectionMetrics(ConnectivityModelFactory.emptyConnectionMetrics())
                        .sourceMetrics(ConnectivityModelFactory.emptySourceMetrics())
                        .targetMetrics(ConnectivityModelFactory.emptyTargetMetrics())
                        .build();
        expectMsg(metricsResponse);
    }};
}