The OCI Distribution spec repo provides go tests that will verify an OCI Registry conformance to the spec.
This nix flake will build the tests and exposes the parameters it takes. You can use the flake on its own to test a registry on 127.0.0.1:3001 by running nix run or nix run .#conformanceTest.
You can also use the conformance package on its own to pass your own parameters.