As described at https://labs.sparebank1.no/2017/10/09/visuell-regressiontestning-i-praktiken/
$ npm install
- html document under test: ./htdocs/.
- test suites: ./visual-tests/specs/.
- baseline screen shots: ./visual-tests/screens/.
- test report ./gemini-report/ (not under version control).
$ npm test
$ npm run update