### Question:
PreferencesUsageDataStore { public void clear() { Preferences prefs = Preferences.userRoot().node(USAGE_PATH); try { prefs.removeNode(); prefs.flush(); } catch (BackingStoreException e) { LOG.error("Unable to clear modules usage statistics", e); } } PreferencesUsageDataStore(); void incrementUsageFor(String moduleId); List<ModuleUsage> getUsages(); void clear(); long getTotalUsage(); @EventListener void onShutdown(ShutdownEvent event); void flush();  }### Answer:
@Test public void testClear() { victim.incrementUsageFor("moduleId"); victim.clear(); assertTrue(isBlank(Preferences.userRoot().node(PreferencesUsageDataStore.USAGE_PATH).node("moduleId") .get(PreferencesUsageDataStore.MODULE_USAGE_KEY, ""))); }