    @Test
    public void testReadQueueLength() {

        System.out.println("testReadQueueLength");
        
        DefaultMetricsReader reader = new DefaultMetricsReader();
        MetricValue value = reader.readValue(MetricName.QUEUE_LENGTH);
        
        assertThat(value, notNullValue());
        assertThat(value.getUnit(), equalTo(MetricUnit.TUPLES));
        assertThat(value.getValue(), greaterThanOrEqualTo(0.0));
    }