static void expectException(Class exceptionType, Runnable r) {
  try {
    r.run();
  } catch e {
    e = unwrapTrivialExceptionWraps(e);
    if (!isInstance(exceptionType, e))
      fail("Wrong exception type, was expecting " + exceptionType, e);
    silentException(e);
    ret;
  }
  fail("No exception thrown!");
}