Because web scripts are not served with an explicit content type encoding, they are interpreted as ISO-8859-1.

So it looks like this when we use translation gadget when running with accessing the HTTP server from runUnitTest :

This is because runUnitTest's server uses iso-8859-15 as default encoding for responses, so the HTML page is served as Content-Type: text/html; charset=iso-8859-15 and later included javascript are also interpreted as this encoding.

Setting default response encoding to utf-8 in runUnitTest is enough to fix the visual glitch in the app, but when viewing the javascript source in the browser, we can see that there's another issue, so we also change the helper scripts to serve javacsripts, css and manifests with an explicit utf8 encoding.