I added a small feature to web-platform-tests that allows you to load a test automatically on the www subdomain by using a .www filename flag (here’s the original issue).

So like, if you ever need to load a page on a different subdomain to test some kind of origin-y or domainy-y thing, you can just name your test something amazing like origin-y-test.www.html and it will open the test for you at www.web-platform.test (rather than web-platform.test, or similarly, however your system or server is configured).

Now you’ll never need to embed an <iframe> or call window.open() ever again (unless you actually need to do those things).

🎃