Testing server errors does not require a real failure — you can simulate any HTTP status code using page.route.
Status code simulation (route.fulfill({ status: 500 })) responds to the request as an internal server error. A correctly written UI should catch this state and display an error banner.
page is already available. Intercept the request to /api/save, respond with 500, then click the «Save» button to trigger the error banner.
Different valid solutions are accepted — full path, glob pattern, or an additional body.