How to intentionally throw an error in injected code with Selenium?

Question

I have a page with custom window.addEventListener("error", ...) logic. I'd like to test that it works, and the only real way to do so is to throw an error.

I tried this:

await browser.executeScript("throw new Error();");

...but Selenium itself saw the error and considered it an exception. Fine.

JavascriptError: Error

  at Object.throwDecodedError (node_modules/selenium-webdriver/lib/error.js:550:15)
  at parseHttpResponse (node_modules/selenium-webdriver/lib/http.js:542:13)
  at Executor.execute (node_modules/selenium-webdriver/lib/http.js:468:26)

Next, tried doing that asynchronously:

await browser.executeScript(() => {
    setTimeout(() => { throw new Error(); }, 1);
});

...but the page itself didn't notice the error (and yes, I've validated that throwing one in the dev tools triggers the expected handling).

Next, I tried using an async script that schedules an error and then the callback:

await browser.executeAsyncScript((callback) => {
    setTimeout(
        () => {
            setTimeout(callback, 1);

            throw new Error();
        },
        1);
});

...but the page itself still didn't notice the error.

Am I missing something here?

Answer 1

You can easily simulate that using below script

var errorElem = document.createElement("script");
errorElem.textContent = 'throw new Error("simulated error");'
document.body.append(errorElem);

This should be able to simulate the event