Matrix Builds for Multiple Environments

Welcome to a powerful feature in GitHub Actions: Matrix Builds! Imagine needing to test your code across many different environments, like various operating systems or programming language versions.

Instead of creating a separate workflow for each combination, matrix builds let you define a set of variables, and GitHub Actions will automatically run your jobs for every possible combination of those variables.

Matrix builds are incredibly useful for:

• Cross-Platform Testing: Ensuring your application works on Windows, macOS, and Linux.
• Multi-Version Compatibility: Testing against different versions of Node.js, Python, or your database.
• Parallel Execution: Running all these tests simultaneously, saving a lot of time.

They help you achieve wider test coverage efficiently.

You define a matrix within the strategy section of a job. Inside strategy.matrix, you list one or more variables, each with an array of values.

GitHub Actions then creates a job for each combination. Let's see how it looks:

In the previous snippet, we defined a node-version variable with three values: 14, 16, and 18.

This single job definition will trigger three separate jobs, each running on ubuntu-latest but using a different Node.js version. This ensures your project works across these versions.

You're not limited to just one variable! You can combine multiple variables in your matrix. For example, you might want to test different operating systems with different Node.js versions.

Just add more key-value pairs under strategy.matrix. The total number of jobs will be the product of the number of values for each variable.

Here’s how to set up a matrix to test on both Ubuntu and Windows, across Node.js versions 16 and 18.

This will create 2 (OS) * 2 (Node.js versions) = 4 separate jobs.

Sometimes you need specific combinations that aren't covered by the default Cartesian product, or you want to add extra variables for certain builds. Use include to add new matrix entries.

For instance, maybe you want to run an additional test only on Ubuntu with Node.js 14, or pass a specific environment variable to a particular OS/version combo.

What if you have a combination that's known to fail, or isn't relevant to your project? The exclude keyword allows you to remove specific configurations from your matrix.

This helps you avoid unnecessary job runs and focus on relevant test cases.

Within your job steps, you can access the current matrix variable values using the ${{ matrix.variable_name }} syntax. This is crucial for configuring tools or running commands specific to each matrix combination.

For example, ${{ matrix.os }} dynamically sets the runner operating system, and ${{ matrix.node-version }} configures the Node.js setup action.

Matrix builds are powerful for:

• Library Development: Testing against multiple versions of a dependency.
• Multi-Language Projects: Building/testing components written in different languages or compilers.
• Browser Compatibility: If using a tool that supports it, testing web apps across different browsers.

They streamline complex testing scenarios into concise, maintainable workflows.

Consider a GitHub Actions workflow that uses a matrix strategy. The matrix is defined as:

strategy:
  matrix:
    os: [ubuntu-latest, macos-latest]
    python-version: [3.8, 3.9]
    exclude:
      - os: macos-latest
        python-version: 3.8

How many jobs will be created by this matrix configuration?

Great job! You've learned about GitHub Actions Matrix Builds.

• They allow you to run jobs for multiple combinations of variables (OS, language versions, etc.).
• Defined using strategy.matrix within a job.
• include adds specific combinations, while exclude removes them.
• Variables are accessed via ${{ matrix.variable_name }}.

Matrix builds are essential for efficient, comprehensive testing across diverse environments. Keep practicing to master them!