Parallel Test Shards
Install dependencies once, then fork into parallel sandboxes to shard work across them.
Install dependencies once, then fork the sandbox into N independent copies that each run a shard of the test suite in parallel — cutting wall-clock time roughly by the number of shards, without repeating the install in every shard.
Setup
Start OpenSandbox in Docker (one-time setup):
bunx alineo-cli initRun it
What it does
Creates one base sandbox, installs pytest, and writes three small test files to it.
Calls base.fork() three times — each fork branches off the base sandbox's state, so none of
them repeat the pip install.
Runs a different test file in each fork with Promise.all, in parallel.
Aggregates each shard's exit code and a one-line summary into an overall pass/fail report.
Generalizing to a real repo
Install dependencies and discover shard boundaries once in the base sandbox, then fork once per
shard (or per CPU core) instead of paying setup cost N times. See Forking
Sandboxes for the underlying sb.fork() primitive.
Server proxy
All examples default to useServerProxy: true — traffic routes through the OpenSandbox server so
Docker bridge IPs don't need to be reachable directly. Set USE_SERVER_PROXY=false to disable
(e.g. when using uvx opensandbox-server on the host).