GitHub Actions makes it easy to automate software builds, tests, and deployments right from GitHub. Any time code is pushed to a repository, Actions can run jobs that build, test, deploy, or nearly anything else you can script. This allows you to set up continuous integration and deployment (CI/CD) directly in your code repository without needing to provision or manage separate build servers.

The first step is to configure a workflow file in your repository that defines the jobs and steps to run. Workflows use a YAML format and are typically named .yml files stored in the .github/workflows directory. For example, a basic build and test workflow could be defined in .github/workflows/build-and-test.yml.

In the workflow YAML, you define a “jobs” section with individual “build” and “test” jobs. Each job specifies a name and runs on a specific operating system – typically Linux, macOS, or Windows. Within each job, you define “steps” which are individual commands or actions to run. Common steps include actions to check out the code, set up a build environment, run build commands, run tests, deploy code, and more.

For the build job, common steps would be to checkout the source code, restore cached dependencies, run a build command like npm install or dotnet build, cache artifacts like the built code for future jobs, and potentially publish build artifacts. For the test job, typical steps include restoring cached dependencies again, running tests with a command like npm test or dotnet test, and publishing test results.

Along with each job having operating system requirements, you can also define which branches or tags will trigger the workflow run. Commonly this is set to just the main branch like main so that every push to main automatically runs the jobs. But you have flexibility to run on other events too like pull requests, tags, or even scheduled times.

Once the workflow is defined, GitHub Actions will automatically run it every time code is pushed to the matching branches or tags. This provides continuous integration by building and testing the code anytime changes are introduced. The logs and results of each job are viewable on GitHub so you can monitor build failures or test regressions immediately.

For continuous deployment, you can define additional jobs in the workflow to deploy the built and tested code to various environments. Common deployment jobs deploy to staging or UAT environments for user acceptance testing, and production environments. Deployment steps make use of GitHub Actions deployment actions or scripts to deploy the code via technologies like AWS, Azure, Heroku, Netlify and more.

Deployment jobs would restore cached dependencies and artifacts from the build job. Then additional steps would configure the target environment, deploy the built artifacts, run deployment validation or smoke tests, and clean up resources after success or failure. Staging deployments can even trigger deployment previews that preview code changes before merging into production branches.

You have flexibility in deployment strategies too, such as manually triggering deployment jobs only when needed, automatic deployment on branch merges, or blue/green deployments that mitigate downtime. Secret environment variables are used to securely supply deployment credentials without checking sensitive values into GitHub. Rolling back deployments is also supported through manual job runs if needed.

GitHub Actions makes CI/CD setup very approachable by defining everything in code without additional infrastructure. Workflows are reusable across repositories too, so you can define templates for common tasks. A robust set of pre-built actions accelerate development through automated tasks for common languages and platforms. Actions can also integrate with other GitHub features like pull requests for code reviews.

GitHub Actions streamlines continuous integration and deployment entirely in GitHub without separate build servers. Defining reusable workflows in code enables automated building, testing, and deploying of applications anytime changes are introduced. Combined with GitHub’s features for code hosting, it provides developers an integrated workflow for optimizing code quality and delivery through every stage of the development process.