when(req.getPathInfo()).thenReturn(ACCESS_TOKEN_PATH);
    when(req.getMethod()).thenReturn("GET");
    Map<String, String[]> params = getDoExchangeTokenParams();
    when(req.getParameterMap()).thenReturn(params);
    doThrow(new URISyntaxException("", "")).when(validator).validateMessage(
        any(OAuthMessage.class), any(OAuthAccessor.class));
    servlet.doGet(req, resp);
    verify(validator).validateMessage(any(OAuthMessage.class), any(OAuthAccessor.class));