nektos/act
Act
This tool is a command-line runner that executes automation workflows locally within isolated container environments. By parsing workflow definition files and translating them into executable shell scripts, it allows developers to validate pipeline logic and configuration changes directly on their machines before committing code to a remote repository.
The runner distinguishes itself by providing a simulation engine that mimics remote CI triggers and event payloads, enabling the testing of complex conditional logic without requiring cloud infrastructure. It supports granular control over the execution environment, allowing users to specify custom container images, inject secrets, and map local directory structures to ensure consistent module resolution. Furthermore, it facilitates integration with private enterprise infrastructure by supporting secure authentication and custom container engine configurations.
The project provides operational controls for troubleshooting, such as the ability to isolate and execute individual workflow tasks by name. It manages the lifecycle of ephemeral runner instances through standard socket interfaces, ensuring that local development environments remain synchronized with the requirements of production pipelines.