@Test
  public void testCloseCancelsAllKeysAndStopsPolling() throws IOException {
    Key key1 = watcher.register(createDirectory(), ImmutableList.of(ENTRY_CREATE));
    Key key2 = watcher.register(createDirectory(), ImmutableList.of(ENTRY_DELETE));

    assertThat(key1.isValid()).isTrue();
    assertThat(key2.isValid()).isTrue();
    assertThat(watcher.isPolling()).isTrue();

    watcher.close();

    assertThat(key1.isValid()).isFalse();
    assertThat(key2.isValid()).isFalse();
    assertThat(watcher.isPolling()).isFalse();
  }
Tests for {@link PollingWatchService}.

@author Colin Decker
jimfs/src/test/java/com/google/common/jimfs/PollingWatchServiceTest.java