nightwatch 画面テストでJavascriptエラーを検知する方法

MEMO.md

http://daipresents.com/2012/post-4906/

HTML側に

<script type="text/javascript">
window.jsErrors = [];
window.onerror = function(errorMessage) {
  window.jsErrors[window.jsErrors.length] = errorMessage;
}
</script>

nightwatch側に

        client
            .url("https://pc3.parseapp.com/app.html")
            .execute(function(data) {
                return window.jsErrors;
            }, [null], function(result) {
                client.assert.equal(result.value.length, 0, "num script error should be 0");
            });