### Question:
NetworkIslService { public void islDown(Endpoint endpoint, IslReference reference, IslDownReason reason) { log.debug("ISL service receive FAIL notification for {} (on {})", reference, endpoint); IslFsm islFsm = locateController(reference).fsm; IslFsmContext context = IslFsmContext.builder(carrier, endpoint) .downReason(reason) .build(); controllerExecutor.fire(islFsm, IslFsmEvent.ISL_DOWN, context); } NetworkIslService(IIslCarrier carrier, PersistenceManager persistenceManager, NetworkOptions options); @VisibleForTesting  NetworkIslService(IIslCarrier carrier, PersistenceManager persistenceManager, NetworkOptions options,
                      NetworkTopologyDashboardLogger.Builder dashboardLoggerBuilder, Clock clock); void islSetupFromHistory(Endpoint endpoint, IslReference reference, Isl history); void islUp(Endpoint endpoint, IslReference reference, IslDataHolder islData); void islDown(Endpoint endpoint, IslReference reference, IslDownReason reason); void islMove(Endpoint endpoint, IslReference reference); void roundTripStatusNotification(IslReference reference, RoundTripStatus status); void bfdStatusUpdate(Endpoint endpoint, IslReference reference, BfdStatusUpdate status); void bfdEnableDisable(IslReference reference, IslBfdFlagUpdated payload); void islDefaultRuleInstalled(IslReference reference, InstallIslDefaultRulesResult payload); void islDefaultRuleDeleted(IslReference reference, RemoveIslDefaultRulesResult payload); void islDefaultTimeout(IslReference reference, Endpoint endpoint); void remove(IslReference reference);  }### Answer:
@Test public void setIslUnstableTimeOnPortDown() { setupIslStorageStub(); IslReference reference = prepareActiveIsl(); Instant updateTime = clock.adjust(Duration.ofSeconds(1)); service.islDown(endpointAlpha1, reference, IslDownReason.PORT_DOWN); Isl forward = lookupIsl(reference.getSource(), reference.getDest()); Assert.assertEquals(updateTime, forward.getTimeUnstable()); Isl reverse = lookupIsl(reference.getDest(), reference.getSource()); Assert.assertEquals(updateTime, reverse.getTimeUnstable()); }
@Test public void portDownOverriderBfdUp() { setupIslStorageStub(); IslReference reference = prepareBfdEnabledIsl(); reset(dashboardLogger); service.islDown(reference.getSource(), reference, IslDownReason.PORT_DOWN); verify(dashboardLogger).onIslDown(reference); }