The jsdom package is causing slowparse failures on SVG and (implicitly) self-closing elements. They're known-fails for now, but they should become passes, so this probably requires using not-jsdom or a headless browser.
Failing tests caused by bugs/incompletions in jsdom. ref: https://github.com/tmpvar/jsdom/issues/705 ref: https://github.com/tmpvar/jsdom/issues/706
Created attachment 8350863 [details] [review] https://github.com/mozilla/thimble.webmaker.org/pull/336 and now all unit tests pass.
Commit pushed to master at https://github.com/mozilla/thimble.webmaker.org https://github.com/mozilla/thimble.webmaker.org/commit/0b2bd015d5336144dfd7ae29c131230aacf23236 Merge pull request #336 from Pomax/bug952509 fix + jsdom deferral