Pester is a test and mock framework for PowerShell.
Pester addresses the need for structured testing in PowerShell environments by providing a framework for writing and executing tests using both traditional assertion-based and behavior-driven development styles. The framework supports mocking, allowing developers to isolate units of code and verify their behavior in controlled conditions. Tests are written in PowerShell itself and can be executed through the command line or integrated into development environments like VSCode.
Pester suits teams building PowerShell automation, infrastructure code, or administrative scripts who want to ensure reliability through automated testing. It works across Windows, Linux, and macOS wherever PowerShell runs, and is compatible with Windows PowerShell 5.1 and PowerShell 7.4 and newer. The framework is particularly valuable for those already invested in PowerShell who need native testing capabilities without adopting external tools or languages.
The project maintains an active contributor community with a structured approach to onboarding. Issues are labeled to guide new contributors, distinguishing between good first issues intended to be straightforward and more complex ones requiring discussion. The maintainers have published a contributor guide and actively solicit help from the community. The project uses code signing with DigiCert certificates and maintains compatibility across multiple PowerShell versions and operating systems.
