# Juju > Juju is an open source orchestration engine for deploying, integrating, and managing applications across Kubernetes, VMs, and bare metal using software operators called charms. 2026 CC-BY-SA, Canonical Ltd. ## Pages in this subsection - [Write a unit test](https://documentation.ubuntu.com/juju/4.0/contributor/howto/write-a-unit-test.md): Learn how to write unit tests for Juju using gocheck, including creating test files, suites, and implementing effective test patterns. ## Optional - [Top-level llms.txt](https://documentation.ubuntu.com/juju/4.0/llms.txt): Complete documentation index.