AdMob set test devices doesn't seem to work

[maxximee]

I've integrated the admob plugin in my app and it works with the google test unit ids.
When I switch to my real ads I get this error no matter what:
JS: bannerad failed to load Error: No ad config.
It seems like an error because I need to register my device as test device. I've added (tried multiple ids here as doc is not clear on what the device id is. Tried device advertising id and device id from adb devices:

const requestConfiguration: RequestConfiguration = { testDevices: ['8e368dc3-00a4-4251-bf6a-d768e4c35053'] };

And in my contructor call:

firebase().admob().setRequestConfiguration(requestConfiguration);

But it doesn't seem like it's doing anything (nothing shows in the logs).
According to google doc, there should be a "AdRequest.isTestDevice()": https://developers.google.com/android/reference/com/google/android/gms/ads/AdRequest#enable_test_devices
But it doesn't seem to be in the plugin.