connecting to an insecure local docker registry in uncontrolled CI environment

I'm building a microservice that performs operations on a docker registry.

The microservice i'm building has a test which starts a docker-registry via the docker-registry image in Docker Hub, so the microservice can connect to it, set it up, work on it etc...

The test fails in CI: The Docker client can't connect to the test-registry because it's insecure. This is in CI, and dynamic, different random ip/port each time, and the docker daemon is used by other parallel tests... so having the test edit the global jsons and restarting docker daemon seems like a bad solution.

Has anyone solved this? how do you test integration with docker-registry in CI? am i doomed to modify the global docker jsons and restart/trigger reload of config?

Some specifics: The build tool is Bazel and runs in GCB so the test itself runs in RBE workers on the Google cloud which are isolated and don't have network access when running the tests and i can't really configure too much, it's not my machine, it's a radon machine each time for each test etc...