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Pester is the de-facto unit testing and mocking framework for PowerShell, widely used to validate scripts, modules, and automation workflows. 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. For teams, Pester encourages test-driven development and makes PowerShell deliverables more maintainable and trustworthy.
Features
- Rich assertion library (e.g. Should -Be, Should -Exist, etc.) for specifying expected behavior in tests
- Built-in mocking support to replace or stub out functions or commands during tests
- Code coverage measurement, with export support (e.g. JaCoCo format) for integration in CI/CD
- Test runner capable of producing formatted output, integrating with Visual Studio Code / other tools
- Compatible with multiple versions of PowerShell (Windows PowerShell 5.1, PowerShell 7.x, etc.)
- Signed releases / security aware (certificate changes handled, publisher signing)
Project Samples
