public void triggerRemoveOne(final String selectorId, final Upstream upstream) {
        removeFromMap(healthyUpstream, selectorId, upstream);
        removeFromMap(unhealthyUpstream, selectorId, upstream);
    }
@Test
    public void testTriggerRemoveOne() {
        final String selectorId = "s1";
        Upstream upstream = mock(Upstream.class);
        healthCheckTask.triggerAddOne(selectorId, upstream);
        healthCheckTask.triggerRemoveOne(selectorId, upstream);
        assertThat(healthCheckTask.getHealthyUpstream().get(selectorId).size(), is(0));

        healthCheckTask.triggerAddOne(selectorId, upstream);
        healthCheckTask.triggerRemoveOne(selectorId, upstream);
        assertThat(healthCheckTask.getHealthyUpstream().get(selectorId).size(), is(0));
    }