Boost Your CI/CD: A Step-by-Step Guide to Running GitHub Actions Locally
GitHub Actions has revolutionized how we automate software workflows, from simple builds and tests to complex multi-stage deployments. However, the traditional CI/CD feedback loop can be a significant bottleneck. Pushing a minor change, waiting for the runner to pick up the job, and then sifting through logs to debug a failed step is a time-consuming process.
What if you could test and debug your workflows instantly, right from your local machine? Running your GitHub Actions locally shatters this slow cycle, enabling faster iteration, more efficient debugging, and significant cost savings. This guide will walk you through how to achieve this using a powerful open-source tool.
The Core Benefits of Local Workflow Testing
Before diving into the “how,” let’s clarify the “why.” Shifting your workflow testing to a local environment provides several powerful advantages:
- Drastically Faster Feedback: Instead of waiting minutes for a remote runner, you can get immediate feedback on syntax errors or failed steps. This accelerates the development and debugging process immensely.
- Cost Efficiency: Each minute on a GitHub-hosted runner consumes your allotted free minutes or costs real money. Running workflows locally costs you nothing, saving your precious runner minutes for genuine production-level integrations and deployments.
- Enhanced Debugging: Debugging in a remote environment can be cumbersome. Locally, you have direct access to logs, artifacts, and the containerized environment, making it much easier to diagnose and fix issues.
- Offline Development: You can continue to build and refine your CI/CD pipelines even without an internet connection, ensuring productivity is never interrupted.
Meet act: Your Local GitHub Actions Runner
The key to unlocking local workflow execution is a popular open-source project called act. This command-line tool reads your GitHub Actions workflow files (the .yml files in your .github/workflows directory) and executes the jobs using Docker containers.
Essentially, act simulates the GitHub Actions environment on your local machine. It pulls or builds the necessary Docker images to mimic the official runners (like ubuntu-latest), allowing your jobs to run in an isolated and consistent environment.
Getting Started: Installation and Setup
To begin, you need one critical prerequisite installed and running on your system: Docker. act relies entirely on Docker to create the containers where your workflow jobs will execute. Ensure Docker Desktop or the Docker daemon is active before proceeding.
With Docker ready, you can install act using the package manager for your operating system:
- macOS (via Homebrew):
bash
brew install act
- Windows (via Scoop or Chocolatey):
bash
scoop install act
# or
choco install act-cli
- Linux (via
go installor installer script):
Visit the officialactrepository for the latest installation scripts, but a common method is usinggo:
bash
go install github.com/nektos/act@latest
Putting act to Work: Common Commands
Once installed, navigate to the root directory of your project containing the .github folder. Here are the most essential commands to get you started.
1. List Available Workflows and Jobs
To see a list of all the jobs act has detected in your workflow files, run the list command:
act -l
This will output a table with the Job ID, Job Name, Workflow Name, and Workflow File, which is helpful for targeting specific jobs.
2. Run the Default Event
By default, GitHub Actions are often triggered by a push event. To simulate this and run all the jobs associated with it, simply execute:
act
The first time you run this, act will prompt you to choose a default Docker image to use (a medium-sized image is often a good starting point). It will then pull the image and execute your workflow steps, printing the log output directly to your terminal.
3. Target a Specific Job
If you only want to test a single job within a larger workflow (e.g., a build job), you can target it using its ID from the list command:
act -j build-job-id
4. Trigger a Different Event
Your workflows might be designed to run on events other than push, such as pull_request or workflow_dispatch. You can easily simulate these events by passing the event name as an argument:
act pull_request
Security and Advanced Usage: Handling Secrets
Workflows often require secrets for things like API keys or deployment credentials. Committing secrets to your repository is a major security risk. act provides a secure way to handle this locally.
Never hardcode secrets in your workflow files. Instead, you can pass them to act at runtime using the --secret flag:
act --secret GITHUB_TOKEN=my-secret-token
For multiple secrets, it’s more practical to use a secret file. Create a file named .secrets (and be sure to add .secrets to your .gitignore file), with each secret on a new line in KEY=VALUE format:
# .secrets file
API_KEY=123456789
DEPLOY_USER=myuser
Now, you can run your workflow using this file:
act --secret-file .secrets
Important Caveats and Limitations
While act is an incredibly powerful tool, it’s important to understand its limitations.
- Environment Parity Is Not Guaranteed:
actdoes an excellent job of simulating the GitHub environment, but it’s not a perfect 1:1 replica. The underlying operating system, network configuration, and installed system libraries on your machine may differ from GitHub’s hosted runners. - Platform-Specific Jobs: If your workflow specifies
runs-on: macos-latest, you won’t be able to run it withacton a Windows or Linux machine without advanced Docker configurations. The base environment must be compatible.
For these reasons, you should always consider act a development and debugging tool, not a complete replacement for a final test run on GitHub before merging critical changes.
By integrating act into your development process, you can build, test, and debug your automation pipelines with greater speed and confidence, transforming your GitHub Actions workflow from a slow, remote process into a fast, interactive local one.
Source: https://centlinux.com/run-github-actions-locally/
