Pester
Pester is the ubiquitous test and mock framework for PowerShell
...It provides a readable DSL for writing Describe/Context/It style specs, expressive assertion helpers (Should), and facilities for setup/teardown to keep tests isolated and reproducible. Beyond unit tests, Pester supports integration tests and can mock functions and modules so external side effects (network, registry, file system) are faked during runs. It integrates with CI systems easily—returning standard exit codes and generating NUnit/JUnit-style test reports—so PowerShell codebases can be validated in automated pipelines. The framework evolves with PowerShell itself, adding features for parallel execution, code coverage measurement, and test discovery to meet production needs. ...