### Question:
BaseStageModel { protected final void sendEmptyResponse() { doSendResponse(EMPTY_DATA); } protected  BaseStageModel(AndroidComponentDelegate androidComponentDelegate); protected  BaseStageModel(@Nullable Activity activity); protected  BaseStageModel(@NonNull ClientCommunicator clientCommunicator, InternalData senderInternalData); String getFlowInitiatorPackage(); Observable<FlowEvent> getEvents(); @NonNull abstract String getRequestJson(); @NonNull ObservableActivityHelper<AppMessage> processInActivity(Context context, Class<? extends Activity> activityClass); @NonNull ObservableActivityHelper<AppMessage> processInActivity(Context context, Intent activityIntent, String requestJson); void addAuditEntry(AuditEntry.AuditSeverity auditSeverity, String message, Object... parameters); void sendEvent(FlowEvent flowEvent);  }### Answer:
@Test(expected = IllegalStateException.class) public void shouldOnlyAllowResponseSentOnce() throws Exception { testModel.sendEmptyResponse(); testModel.sendEmptyResponse(); }