The `agent-testability.spec.ts` tests were hardcoding the relay URL to `http://127.0.0.1:8878`, which caused `ECONNREFUSED` errors when running in parallel because the test fixture allocates dynamic ports to avoid collisions.
This commit updates the tests to use the dynamic `httpUrl` provided by the relay fixture.
Co-authored-by: PR0M3TH3AN <[email protected]>