So I converted another old gallery module (gallery-datatable-formatters) per the "New Gallery Integration" writeup ... including yogi update. Everything went fine, apparently.
I upgraded my code, added tests, etc..
I noticed in the tests/unit/index.html (that was created by yogi update) that the following was set;
filter: (window.location.search.match(/[?&]filter=([^&]+)/) || ) || 'raw'
when I ran the test coverage report (and also with istanbul) I got the "NaN%" stuff. After awhile, I checked the instrumentation file at /build/../gallery-datatable-formatters-coverage.js and noticed it
used a different "_yuitest_coverage" setup.
So when I went back to my index.html and changed this,
It worked fine, gave proper coverage statistics.
So in my case I think yogi update incorrectly setup the tests/unit/index.html with the wrong coverage flag.
Might be a bug possibly in yogi update, not sure if it still fixes my #35, or hatch's #44 or #45
Fixes #46, set the proper name on the coverage modules in default tests
This will be fixed in the next release.