nyc config is not used in browser tests

[yomed]

I'm using nyc as directed, to generate code coverage. My .nycrc file looks like this:

{
  "exclude": [
    "**/test",
    "**/*.marko.js",
    "common/test-utils"
  ],
  "report-dir": "./.coverage",
  "all": true
}

The exclusions work fine on the server testing, but are not respected in browser tests. In the browser tests, even the .marko files get included in coverage, despite any exclusion rules against them.