fesenClient.targetIndices = null;

        when(mockClient.admin()).thenReturn(mockAdminClient);
        when(mockAdminClient.cluster()).thenReturn(mockClusterAdminClient);
        when(mockHealthResponse.isTimedOut()).thenReturn(false);
        when(mockFuture.actionGet(anyLong(), any(TimeUnit.class))).thenReturn(mockHealthResponse);

        // Should not throw NullPointerException
        try {

        final ClusterHealthResponse healthResponse =
                get(c -> c.admin().cluster().prepareHealth(indices).setWaitForYellowStatus().execute());
        if (!healthResponse.isTimedOut()) {
            onConnectListenerList.forEach(l -> {
                try {
                    l.onConnect();
                } catch (final Exception e) {