# Tests {#sec-tests}

Home Manager includes a basic test suite and it is highly recommended to
include at least one test when adding a module. Tests are typically in
the form of \"golden tests\" where, for example, a generated
configuration file is compared to a known correct file.

It is relatively easy to create tests by modeling the existing tests,
found in the `tests` project directory. For a full reference to the
functions available in test scripts, you can look at NMT's
[bash-lib](https://git.sr.ht/~rycee/nmt/tree/master/item/bash-lib).

## Using the tests command {#sec-tests-command}

Home Manager provides a convenient `tests` command for discovering and running tests:

``` shell
# List all available tests
$ nix run .#tests -- -l

# List tests matching a pattern
$ nix run .#tests -- -l alacritty

# Run all tests matching a pattern
$ nix run .#tests -- alacritty

# Run a specific test
$ nix run .#tests -- test-alacritty-empty-settings

# Run integration tests
$ nix run .#tests -- -t -l

# Interactive test selection (requires fzf)
$ python3 tests/tests.py -i

# Pass additional nix build flags
$ nix run .#tests -- alacritty -- --verbose
```

## Manual test commands {#sec-tests-manual}

For advanced usage or CI environments, you can also run tests manually using nix build commands.

The full Home Manager test suite can be run by executing

``` shell
$ nix-build --pure --option allow-import-from-derivation false tests -A build.all
```

in the project root. List all test cases through

``` shell
$ nix-build --pure tests --option allow-import-from-derivation false -A list
```

and run an individual test, for example `alacritty-empty-settings`,
through

``` shell
$ nix-build --pure tests --option allow-import-from-derivation false -A build.alacritty-empty-settings
```

However, those invocations will impurely source the system's Nixpkgs,
and may cause failures. To run against the Nixpkgs from the `flake.lock` file,
use instead e.g.

``` shell
$ nix build --reference-lock-file flake.lock --option allow-import-from-derivation false ./tests#test-all
```

or

``` shell
$ nix build --reference-lock-file flake.lock --option allow-import-from-derivation false ./tests#test-alacritty-empty-settings
```

Some tests may be marked with `enableLegacyIfd`, those may be run by run with e.g.

``` shell
$ nix-build --pure tests --arg enableLegacyIfd true -A build.mytest
```