[kmlx]

can be solved this way:

- npm start when developing

- deploy on dev using the artefacts from npm run build

builds take a bit longer this way, but it guarantees QA will test using a non-dev build

[KronisLV]

> In reality, many users of React test on local and immediately deploy into production.

> deploy on dev using the artefacts from npm run build

These two statements do not fit together.

I agree that "You should have dev/test/staging/... environments" is the correct answer, but clearly that's not the reality for everyone.

[kmlx]

> clearly that's not the reality for everyone

might not be the reality, but multiple envs is the only correct answer.