Development: Region of integration tests cannot be set

Hey all, I hope this is the right place to raise this question but the link to the Slack Community of GCP in the issue template on GitHub seems to be broken.

I am about to raise two PRs to add support for new fields in a GCP resource. However, I of course need to update the tests around the resource. In the test section of the contribution guide, it says that you can control the region in which the integration tests are executed by setting the GOOGLE_REGION environment variable. This variable however seems to be ignored during the execution of the unit tests and the region falls back to a US one. The following environment variables are set:

GOOGLE_ZONE=europe-west1-b
GOOGLE_PROJECT=my-project
GOOGLE_REGION=europe-west1
GOOGLE_CREDENTIALS=./credentials.json

Tests are executed with Make: make testacc TEST=./google TESTARGS='-run=TestAccStorageTransferJob_*'.

Am I somehow missing something that would prevent me from using a European region?

Thanks for the help!