add_scripts.txt

"test": "karma start --coverage",
"test:watch": "karma start --auto-watch=true --single-run=false",
"test:update-snapshots": "karma start --update-snapshots",
"test:prune-snapshots": "karma start --prune-snapshots",
"test:compatibility": "karma start --compatibility all --auto-watch=true --single-run=false"

Commands explained:

`test`: does a single test run on the configured browsers (default headless chrome) and prints tests and coverage results.
`test:watch`: does a single test run, and then re-runs on file changes. coverage is not analyzed for performance. in watch mode you can also visit http://localhost:9876/debug.html to debug in the browser
`test:update-snapshots`: updates any snapshots files from @open-wc/semantic-dom-diff. Use this when your component's rendered HTML changed.
`test:prune-snapshots`: prunes any used snapshots files from @open-wc/semantic-dom-diff.
`test:compatibility`: like test:watch, except that it makes your tests compatible with older browsers (including IE11).


"test": "karma start --single-run --browsers ChromeHeadless karma.conf.js"