Thank you Alexandre.

Would it be worth adding that

<env name="SYMFONY_PHPUNIT_LOCALE" value="0"/>

disable the behavior, since

setlocale(\LC_ALL, 0);

returns the locale instead of setting it

I'm not sure, because this is something that touches the internals of the bridge, which we do not document. Also, if someone wants to disable this new behavior, it'll remove the env var I guess. So I'm not sure this is something we should add as it may bring more confusion than anything else 🤔

Also, if someone wants to disable this new behavior, it'll remove the env var I guess.

No, removing the env var won't disable the behavior, it will set the default?? 'C' locale which doesn't solve my issuesymfony/symfony#52185

By default the bridge set a consistent locale and there was no way to avoid this behavior.
The suggestion was to introduce a env var to disable the behavior:
symfony/symfony#52185 (comment)

Then, we added the feature to select another local.
But personally the reason I introduce this was to disable the feature.

When looking at the bridge issues, some people were complaining about the fact a locale was set, but none complained about the locale set. So this feature might be used more often to disable the behavior rather than changing the locale.