[Question] Fail on unhandled exception?

[tslocke]

If an unhandled JS exception happens in the browser, i.e. an error that would show up in the devtools console, does that cause the current test to fail?

If not, is there a way to make that happen?

Alternatively, I have a "something went wrong" error indicator that pops up in the UI. I know how to write an assertion that says the error indicator is not present, but that only applies at a particular moment in the test script.

Say I'm waiting for some action to complete, I also want to be watching to see if the error appears, and fail the test if it does. How can I code that? e.g. "wait for X to be visible" and simultaneously "fail if Y becomes visible"

Thanks

[tslocke]

I figured out a way to do this. Not sure if it's good practice or not.

I run this as the first line of the test. The key is to wait for the error message, but not with an await, so the script can continue.

page.waitForSelector('.error-message').then(() => expect('But it did').toBe('Error bar not to show up'))

The strings in expect/to-be were just a way to have something meaningful in the report (Expected: "Error bar not to show up" Received: "But it did"). I would rather have a more semantic way to fail the test, e.g. assert(false, "Error message showed up") but I couldn't find anything like that.

[tslocke]

Urgh. This only works for the failure case. If the test "passes", playwright complains that "Target closed" while still waiting for something.

[tslocke]

OK I found page.on('pageerror', ...)

Was nice chatting to me : )

[rwoll]

Closing per above 😄 😁

Yes, page.on('pageerror') is the recommended approach.

[karlhorky]

@rwoll @dgozman @mxschmitt would the Playwright team consider adding a config option for failing on error to Playwright?

I'm aware that the following code achieves "failing on error" to add to every test (also multiple tests at once via overriding the page fixture), but I think this would be widespread enough that some option like failOnPageError or failOnUnhandledException in the Playwright config would make sense.

page.on('pageerror', (error) => {
  throw error;
});

References:

• [BUG] throwing from pageerror callback leads to unpredictable behavior #28056

Prior Art / Similar

• Cypress will fail a test on uncaught exception: "Fires when an uncaught exception occurs in your application. Cypress will fail the test when this fires"
• failOnConsoleLog proposal by @coryhouse [Feature]: Add config setting to fail if the app writes to the console. #27277