fastest
What it does
Section titled “What it does”Many Den integration tests use real NixOS evaluations, so fastest trades a few nix-unit features (no error diff, no expect throws) for raw speed via nix-eval-jobs. It works for both Nix flakes and non flake .nix files, and falls back to nix-unit for traces when a single test is specified.
Key features
Section titled “Key features”- Parallel execution,
nix-eval-jobsruns tests across multiple workers - Flake mode,
--flake <path or path#tests> - File mode,
--file <path> -A <attr> - Optional suite, run everything, or a named subset
- Individual test traces, falls back to
nix-unitfor debugging (--nix-unit) - Auto-detected system, overridable with
-s - Configurable parallelism, 8 workers / 2 GB each by default;
-Pfor all cores
Role in the ecosystem
Section titled “Role in the ecosystem”fastest is the speed-focused testing tool of the ecosystem, a parallel companion to checkmate’s nix-unit integration, born from Den’s own CI needs.