[Feature]: expect(locator).toHaveAccessibleErrorMessage(…)

[MattyBalaam]

🚀 Feature Request

A previous PR added some jest-dom inspired assertions like toHaveAccessibleDescription #18332.

A very good additional would be to also match toHaveAccessibleErrorMessage https://github.com/testing-library/jest-dom#tohaveaccessibleerrormessage

This allows you to assert that an element has the expected accessible error message.

Example

await component.getByLabel('An input').fill('incorrect value');

await expect(component.getByLabel('An input'). toHaveAccessibleErrorMessage('You have entered invalid text');

Motivation

At the moment to accomplish the same thing multiple assertions need to be made to test this common a11y patterns.

Playwright should aim to provide a first-class experience for testing a11y