Blog
Mert Özen's blog posts on software development, backend, frontend, and DevOps.
What Is GitHub Actions? Your First CI with Workflows, Events, Jobs, Steps and Runners
GitHub Actions is a CI/CD platform that runs the YAML workflows under .github/workflows on runners in response to repository events. We write a first workflow that restores, builds and unit-tests the Bookstore API, try it locally with act and actionlint, and cover uses versus run, the run log, re-runs and the reasoning behind the Web API 31 workflow.
Expressions, Contexts and Variables in GitHub Actions: if, outputs and GITHUB_ENV
Expressions inside ${{ }} read values from contexts (github, env, vars, steps, needs, inputs…), use loose comparison and drive if: conditions. With act output we show why text outside ${{ }} in if is always true, the contains/fromJSON/hashFiles/case functions, moving data with GITHUB_OUTPUT and GITHUB_ENV, a test table with GITHUB_STEP_SUMMARY, and always versus !cancelled.
Jobs in GitHub Actions: needs, matrix, concurrency, timeouts and Service Containers
Jobs run in parallel by default; needs builds a DAG, and everything depending on a failed job is skipped. We split the Bookstore CI into format, unit-test (OS matrix), integration-test (PostgreSQL 16/17/18 service container), web-build and publish jobs and run it with act, covering include/exclude, fail-fast, max-parallel, concurrency, timeout-minutes, continue-on-error and the service command/entrypoint keys from April 2026.
.NET CI with GitHub Actions: setup-dotnet, global.json, NuGet Cache, Test Reports and Coverage
In a .NET 10 CI, pin the SDK with global.json and setup-dotnet@v6, restore with lock files and --locked-mode, key the NuGet cache to the lock hash, and gate with dotnet format and -warnaserror. We produce TRX and Cobertura reports with xUnit v3 on Microsoft.Testing.Platform, write them to the job summary and keep them with upload-artifact, and show act's v7 artifact limit and the Linux file-name pitfall with real output.
Reading Old GitHub Actions Workflows: From set-output to GITHUB_OUTPUT, From Node 12/16/20 to Node 24
When updating an old workflow, change the runner label, action majors, SDK source, workflow commands and cache key together: ubuntu-18.04, @v2 actions and ::set-output either no longer work or warn in 2026. A 2018–2026 timeline, the Node 12→24 transitions, actionlint and act output for a 2021-style .NET 5 workflow, a checklist for moving to .NET 10 and a summary of 2026.