Pester
Pester is the ubiquitous test and mock framework for PowerShell
...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. For teams, Pester encourages test-driven development and makes PowerShell deliverables more maintainable and trustworthy.