X_TEST_LIVE_NODE_UPGRADE_REFUSED
Means
the in-process sync node refused the connection
Typical cause
the subscribe fixture's node answered the upgrade with a response instead of taking it — its accept budget, its connection ceiling, or a node that was never started. A different failure from having nothing to serve, which is the row below
Fix
await node.start() before connect(), and keep the request path at /_x/sync