Template: Bug Reproduction

This template helps you create minimal Den reproductions.

Use it for:

Showcasing focused demos of how you are trying to use Den.
Reducing a problem to its minimum outside of your infra.
Sharing code that exposes an unknown bug.
Contributing bug fixes to Den core.

All PRs modifying this template are run by Den CI on the following Den versions: PR_HEAD, main, latest.

Feel free to send any PR even if you don’t know if it is an actual bug or if you don’t know the solution.

Just having an small, focused example can help Den maintainers a lot. We can together determine if there’s something we need to fix in Den.

If you wish to contribute a fix, you are more than welcome, just mention you’d like to work on this at the PR.

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.environment.sessionVariables.FOO = ["foo" "bar"];

        # what you get
        expr = igloo.environment.sessionVariables.FOO;
        # what you expect
        expected = "foo:bar";
      }
    );
  };
}

How denTest Works

denTest is a helper that:

Creates a fresh Den evaluation with your module
Provides helpers like igloo (host config), tuxHm (user’s HM config)
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`
`trace`	traces included aspect names

If you want to see some examples, take a look at other bogus reports that are now part of Den repository at:

ls den/templates/ci/modules/features/deadbugs/*.nix

Run Tests

# From the bogus root
nix flake check

# From the Den root
just bogus

Contributing a Fix

Edit Den /nix or /modules code and run:

just bogus

When your changes to Den have fixed the bug, be sure to move bug.nix into the templates/ci/modules/feautres/deadbugs/ directory, following naming conventions for both the file and test-suite name.

What It Provides

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

Next Steps

Read Debug Configurations for debugging techniques
See the CI Tests template for Den’s own comprehensive test suite

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