GitHub users have been quick to adopt GitHub Actions for automation. But at times, it would be handy to run them locally. Now there is a tool, Act, that can do this! Why would you want to do this? Two reasons:

• Fast Feedback – Rather than having to commit/push every time you want to test out the changes you are making to your .github/workflows/ files (or for any changes to embedded GitHub actions), you can use act to run the actions locally. The environment variables and filesystem are all configured to match what GitHub provides.
• Local Task Runner – I love make. However, I also hate repeating myself. With act, you can use the GitHub Actions defined in your .github/workflows/ to replace your Makefile!

How does this work?

When you run act it reads in your GitHub Actions from .github/workflows/ and determines the set of actions that need to be run. It uses the Docker API to either pull or build the necessary images, as defined in your workflow files and finally determines the execution path based on the dependencies that were defined. Once it has the execution path, it then uses the Docker API to run containers for each action based on the images prepared earlier. The environment variables and filesystem are all configured to match what GitHub provides.

There are versions for Windows, Mac, and Linux. Docker is required. See the Act GitHub repo for all the details.