### Question:
GlusterWatchKey implements WatchKey { public boolean update() { DirectoryStream<Path> paths; try { paths = Files.newDirectoryStream(path); } catch (IOException e) { return false; } List<Path> files = new LinkedList<>(); boolean newEvents = false; for (Path f : paths) { newEvents |= processExistingFile(files, f); } for (Path f : events.keySet()) { newEvents |= checkDeleted(files, f); } return newEvents; }  @Override boolean isValid(); boolean update(); @Override synchronized List<WatchEvent<?>> pollEvents(); @Override synchronized boolean reset(); @Override void cancel(); @Override Watchable watchable();  }### Answer:
@Test public void testUpdate_whenIOException() throws IOException { PowerMockito.mockStatic(Files.class); when(Files.newDirectoryStream(mockPath)).thenThrow(new IOException()); assertFalse(key.update()); PowerMockito.verifyStatic(); Files.newDirectoryStream(mockPath); }