CONSOLE MESSAGE: line 5: Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'none'". CONSOLE MESSAGE: line 5: Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'none'". Check that a CSP header added by a 304 response does not override one from the original request. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". Check that the nonce is the same, meaning that the document was only generated once: PASS frame1.contentDocument.querySelector("input").value == frame2.contentDocument.querySelector("input").value is true PASS successfullyParsed is true TEST COMPLETE