Browserstack launcher: "WebDriver Error: Timed out waiting for asyncrhonous script" on iOS devices

[gruhn]

Bug Description

When I run tests on iOS devices (iPhone/iPad) using the Browserstack launcher AND in the web-test-runner config concurrency is set to something >1, then I get the following error:

[Browserstack] Setting up Browserstack Local proxy...

2024-04-19T12:25:59.180Z ERROR webdriver: Request failed with status 500 due to WebDriver Error: Timed out waiting for asyncrhonous script result after 0 ms
index.html:

 ❌ WebDriver Error: Timed out waiting for asyncrhonous script result after 0 ms
    WebDriver Error: Timed out waiting for asyncrhonous script result after 0 ms
        at getErrorFromResponseBody (file:///Users/niklas.gruhn/Workspace/demo-browserstack-iphone-timeout/node_modules/webdriver/build/utils.js:195:12)
        at NodeJSRequest._request (file:///Users/niklas.gruhn/Workspace/demo-browserstack-iphone-timeout/node_modules/webdriver/build/request/index.js:193:23)
        at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
        at async Browser.wrapCommandFn (file:///Users/niklas.gruhn/Workspace/demo-browserstack-iphone-timeout/node_modules/@wdio/utils/build/shim.js:90:29)
        at async Browser.wrapCommandFn (file:///Users/niklas.gruhn/Workspace/demo-browserstack-iphone-timeout/node_modules/@wdio/utils/build/shim.js:90:29)
        at async IFrameManager.stopSession (/Users/niklas.gruhn/Workspace/demo-browserstack-iphone-timeout/node_modules/@web/test-runner-webdriver/dist/IFrameManager.js:95:29)

In the Browserstack web UI I can see that the tests were successfully executed. The error only occurs when closing the session. This is the "asynchrones script" that is timing out:

web/packages/test-runner-webdriver/src/IFrameManager.ts

Lines 119 to 138 in efd8579

	const returnValue = await this.driver.executeAsync(`
	var iframe = document.getElementById("${frameId}");
	var testCoverage;
	try {
	testCoverage = iframe.contentWindow.__coverage__;
	} catch (error) {
	// iframe can throw a cross-origin error if the test navigated
	}
	// Don't move on until the iframe has settled after unloading the page
	var done = arguments[arguments.length-1];
	var loaded = function() {
	iframe.removeEventListener('load', loaded);
	iframe.removeEventListener('error', loaded);
	done({ testCoverage: testCoverage });
	};
	iframe.addEventListener('load', loaded);
	iframe.addEventListener('error', loaded);
	// set src after retrieving values to avoid the iframe from navigating away
	iframe.src = "about:blank";
	`);

In particular, it seems like the load event on the iframe is never fired.

To Reproduce

I setup this repository with a minimal demo. Unfortunately, Browserstack credentials are required. To reproduce: pull the repository and run:

export BROWSERSTACK_USERNAME="..."
export BROWSERSTACK_ACCESSKEY="..."
npm install
npm test

Workaround

Setting concurrency: 1 in the web-test-runner config.