@sebastian Thanks for the reply! Feel free to answer the editor questions as well. 
@sebastian @grigorious Would you mind trying my branch in your project? npm install --save-dev lydell/node-test-runner#js to install, then run the tests like you usually do (assuming you have a local install). I’m interested in (1) if the same amount of tests is run and (2) how long it takes*. I’m expecting a half a second speedup.
* Note that the duration that elm-test reports doesn’t include compilation time, which is what I’ve worked on. Run time npx elm-test 'src/**/*Test.elm' a couple of times before and after you’ve installed my branch to see the full duration.