For input elements with type="number", you have to use "setText" to set negative values.
5. Content Security Policy errors
We are looking for a solution right now. Technically, it's possible to overwrite CSP rules with add-ons, but it would be insecure to do that on every web page.
For now, to work around the issue on Chrome, users can use a third-party add-on (e.g. Disable Content-Security-Policy https://chrome.google.com/webstore/detail/disable-content-security/ieelmcmcagommplceebfedjlakkhpden?hl=en) to disable CSP rules, then execute the test in KR as usual. Don't forget to disable that add-on when unused.
On Firefox, please disable the "security.csp.enable" option in "about:config" to achieve the same effect. Don't forget to enable it when unused.