@Test
    public void testDefaultDomain() {
        String taskType = "test-task";
        String[] domains = new String[] {"domain1", "domain2", "NO_DOMAIN"};

        PollData pollData1 =
                new PollData(
                        "queue1", domains[0], "worker1", System.currentTimeMillis() - 99 * 10000);
        when(executionDAOFacade.getTaskPollDataByDomain(taskType, domains[0]))
                .thenReturn(pollData1);
        when(executionDAOFacade.getTaskPollDataByDomain(taskType, domains[1])).thenReturn(null);
        String activeDomain = workflowExecutor.getActiveDomain(taskType, domains);
        assertNull(activeDomain);
    }
Simulate Queue push failures and assert that scheduleTask doesn't throw an exception.
core/src/test/java/com/netflix/conductor/core/execution/TestWorkflowExecutor.java