### Question:
InMemoryAlertManager implements AlertManager { @Override public Alert remove(Alert.ID id) { try { this.alertsLock.writeLock().lock(); AtomicReference<GenericAlert> ref = this.alertsById.remove(id); if (ref != null) { this.alertsByTime.values().remove(ref); return ref.get(); } else { return null; } } finally { this.alertsLock.writeLock().unlock(); } } InMemoryAlertManager(); @Override ID getId(); void setReceiversExecutor(Executor receiversExecutor); @Override Set<AlertDescriptor> getAlertDescriptors(); void setAlertDescriptors(Collection<AlertDescriptor> types); @Override void updateLastUpdatedTime(); @Override boolean addDescriptor(AlertDescriptor descriptor); @Override void addReceiver(AlertNotifyReceiver receiver); @Override void removeReceiver(AlertNotifyReceiver receiver); @Override Optional<Alert> getAlert(Alert.ID id); @Override Optional<Alert> getAlertAsServiceAccount(Alert.ID id); @Override AlertCriteria criteria(); @Override Alert.ID resolve(Serializable ser); @Override Iterator<Alert> getAlerts(AlertCriteria criteria); @Override Iterator<AlertSummary> getAlertsSummary(AlertCriteria criteria); @Override Alert create(URI type,String subtype, Alert.Level level, String description, C content); @Override Alert createEntityAlert(URI type, Alert.Level level, String description, EntityIdentificationAlertContent<C> content); @Override AlertResponse getResponse(Alert alert); @Override Alert remove(Alert.ID id); @Override Long getLastUpdatedTime(); @Override EntityIdentificationAlertContent createEntityIdentificationAlertContent(String entityId, SecurityRole.ENTITY_TYPE entityType, C content); static final int MAX_ALERTS; }### Answer:
@Test public void testRemove() { Alert.ID id1 = this.manager.create(URI.create("urn:alert:test1"), "subtype",Alert.Level.INFO, "test1", "content").getId(); Alert.ID id2 = this.manager.create(URI.create("urn:alert:test2"),"subtype", Alert.Level.CRITICAL, "test2", "content").getId(); Alert alert2 = this.manager.remove(id2); Alert alert1 = this.manager.remove(id1); Iterator<? extends Alert> itr = this.manager.getAlerts(null); assertThat(itr.hasNext()).isFalse(); assertThat(alert1.getId()).isEqualTo(id1); assertThat(alert2.getId()).isEqualTo(id2); }