}

  public void testNullCloseable() throws IOException {
    Closer closer = Closer.create();
    closer.register(null);
    closer.close();
  }

  /**
   * Asserts that an exception was thrown when trying to close each of the given throwables and that
   * each such exception was suppressed because of the given thrown exception.
   */
  private void assertSuppressed(Suppression... expected) {