public <W extends T> W get(final Class<W> clazz) {
    return get(clazz, Constants.DEFAULT_REGISTRY_GET_TIMEOUT_MS);
  }
@Test
  public void unavailable() {
    Registry<TestServer, Void> registry = new Registry<>();

    Exception exception = Assert.assertThrows(Exception.class,
        () -> registry.get(ServerB.class, 100));
    Assert.assertTrue(exception.getMessage().contains("Timed out"));
    Assert.assertTrue(exception.getMessage().contains("ServerB"));
  }