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Pterodactyl runs each server as a plain JRE process in its own container with the server files on a mounted volume. The harness in docker-test/ does the same, so what it proves is what a rented network would do rather than what Kubernetes did. It brings up a standalone MongoDB, a Redis, two shards, a hub and a Velocity proxy on one Docker network, and none of the shards are declared in velocity.toml — they register themselves, which is the piece that replaced the Kubernetes operator.

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Running it

Needs Docker and about 6 GB of memory.
The proxy is on localhost:25577. setup.sh downloads the pinned Paper and Velocity builds, generates one world and copies it to each shard, writes the configuration, and assembles a compose file. It is idempotent.

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What it checks

The plugins enable

On the real Paper, Velocity and Java versions, which is the single most likely thing to differ on a host you do not control.

A standalone database works

The read concern adapts and the log says which it chose.

Self-registration

Both shards appear on the proxy from their address alone.

Restart and recovery

Stopping a shard withdraws it and the proxy unregisters it; starting it brings the topology back.
RCON is enabled on the shards, so the operator commands can be driven from a script rather than by hand.

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What it cannot check yet

It cannot walk a player across a border. No headless client speaks this protocol version — node-minecraft-protocol stops one release short — so the crossing, the ghost band, the block mirror and the audit log still need a person with a real client.
The proxy in the harness runs online-mode = false so a test client can connect without a Mojang account. That is the one setting deliberately unlike production; see Security.

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Why this exists

Because a full line-by-line review, a green build and a passing unit suite all missed a null dereference that stopped the plugin enabling at all. Field initializers run before the constructor body, so a setting read from one dereferenced a field that was still null. Every shard failed to enable, Paper disabled the plugin, and the server carried on accepting players while owning nothing. Nothing in the build could see it, because nothing in the build constructs a plugin. Thirty seconds of a real server starting caught it immediately.