--- title: "NixOS first impressions: writing system-level tests" url: https://daily.dev/posts/nixos-first-impressions-writing-system-level-tests-o6sjlaois source_url: https://advancedweb.hu/nixos-first-impressions-writing-system-level-tests type: article source: "Advanced Web Machinery" published: 2026-05-25T15:26:48.601Z updated: 2026-05-25T15:27:32.011Z tags: ["firewall", "nixos"] reading_time: 8 upvotes: 3 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # NixOS first impressions: writing system-level tests **[Advanced Web Machinery](https://daily.dev/sources/advancedweb)** · 8 min read · 3 upvotes · 0 comments ## Summary A developer explores NixOS not through its installer or desktop environment, but by writing system-level tests. The core motivation is NixOS's reproducibility — all packages and configuration are pinned to exact commits — which enables test-driven OS updates: bump dependencies, run tests, only commit if they pass. Two concrete test examples are shown: a firewall test that spins up two VMs (one with firewall enabled, one without) to verify traffic is correctly blocked, and a DNS-over-HTTPS test that intercepts network traffic via a fake resolver to verify correct HTTPS resolution. The author plans to apply this workflow to a laptop with GitHub Actions running periodic dependency bumps and tests before auto-updating the machine. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Why I love NixOS](https://daily.dev/posts/why-i-love-nixos-on18fcwiv) · Hacker News · 3 upvotes · 0 comments - [Building \(systems\) software with Nix](https://daily.dev/posts/building-systems-software-with-nix-jbw3o8thj) · Lobsters · 1 upvotes · 0 comments --- Tags: [#firewall](https://daily.dev/tags/firewall), [#nixos](https://daily.dev/tags/nixos) [View this post on daily.dev](https://daily.dev/posts/nixos-first-impressions-writing-system-level-tests-o6sjlaois)