As we test our polymer elements with web-component-tester (wct), we get a lot of 404 warnings that don't seem to affect the tests but are annoying, such as
firefox 37 ✓ app/elements/twt-comment/test/basic.html » twt-comment » should render the information provided in the `comment.author` binding
404 GET /app/elements/twt-comment/test/undefined
Has anyone seen these? They don't seem to be coming from our own code, and I'm having trouble following the wct code. I'd like to try to get rid of them.
By debugging the test in Chrome dev tools and looking at the referrer of the 404 request, we discovered that a subelement of ours was referring to an invalid image URL. Sorry for the false alarm.