Template: Bug Reproduction

The bogus template helps you create minimal bug reproductions. Use it when reporting issues or contributing fixes.

Initialize

mkdir bogus && cd bogus
nix flake init -t github:vic/den#bogus
nix flake update den

Project Structure

flake.nix
modules/
  bug.nix           # your bug reproduction
  test-base.nix     # test infrastructure (DO NOT EDIT)

Writing a Bug Reproduction

Edit modules/bug.nix with a minimal test case:

{ denTest, ... }:
{
  flake.tests.bogus = {
    test-something = denTest (
      { den, lib, igloo, tuxHm, ... }:
      {
        den.hosts.x86_64-linux.igloo.users.tux = { };

        # set up the scenario
        den.aspects.igloo.nixos.something = true;

        # what you get
        expr = igloo.something;
        # what you expect
        expected = true;
      }
    );
  };
}

How denTest Works

denTest is a helper that:

1. Creates a fresh Den evaluation with your module
2. Provides helpers like igloo (host config), tuxHm (user’s HM config)
3. Compares expr against expected using nix-unit

Available test helpers (from test-base.nix):

Helper	Description
igloo	nixosConfigurations.igloo.config
iceberg	nixosConfigurations.iceberg.config
tuxHm	igloo.home-manager.users.tux
pinguHm	igloo.home-manager.users.pingu
funnyNames	Resolves an aspect for class "funny" and collects .names
show	builtins.trace helper for debugging

Run Tests

nix flake check

Testing Against Different Den Versions

Edit .github/workflows/test.yml to test against multiple Den versions:

strategy:
  matrix:
    rev: ["main", "v1.0.0", "abc1234"]

This helps identify regressions — include "main" and any release tag or commit.

Contributing a Fix

If you’re submitting a fix to Den, test against your local checkout:

cd <den-working-copy>
nix flake check --override-input den . ./templates/bogus

What It Provides

Feature	Provided
nix-unit test infrastructure	✓
Pre-configured denTest helper	✓
Version matrix testing	✓
Common test helpers	✓

Next Steps

• Share your reproduction repo on GitHub Discussions
• Read Debug Configurations for debugging techniques
• See the CI Tests template for Den’s own comprehensive test suite