@Test
public void testSuccessfulHandler() throws IOException {

  String path = "/testSuccessfulHandler";
  boolean[] didRun = {false};
  Handler h = new TestHandler(path, () -> {
    didRun[0] = true;
  });
  instance.addHandler(h);
  doPost(path, path.getBytes(StandardCharsets.UTF_8));
  assertTrue("Handler should have run on " + path, didRun[0]);
}