- Invoke the `.online` attribute with [`nix run`](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-run) ([experimental](https://nixos.org/manual/nix/stable/contributing/experimental-features#xp-feature-nix-command)). This runs outside the sandbox, and checks that both internal and external hyperlinks are correct.
  Example:

  ```shell
  nix run nixpkgs#lychee.tests.ok.online
  ```

### Inputs {#tester-lycheeLinkCheck-inputs}

`site` (path or derivation) {#tester-lycheeLinkCheck-param-site}

: The path to the files to check.

`remap` (attribe set, optional) {#tester-lycheeLinkCheck-param-remap}

: An attribute set where the attribute names are regular expressions.
  The values should be strings, derivations, or path values.

  In the returned check's default configuration, external URLs are only checked when you run the `.online` attribute.

  By adding remappings, you can check offline that URLs to external resources are correct, by providing a stand-in from the file system.

  Before checking the existence of a URL, the regular expressions are matched and replaced by their corresponding values.

  Example:

  ```nix
  {
    "https://nix\\.dev/manual/nix/[a-z0-9.-]*" = "${nix.doc}/share/doc/nix/manual";
    "https://nixos\\.org/manual/nix/(un)?stable" =
      "${emptyDirectory}/placeholder-to-disallow-old-nix-docs-urls";
  }
  ```

  Store paths in the attribute values are automatically prefixed with `file://`, because lychee requires this for paths in the file system.
  If this is a problem, or if you need to control the order in which replacements are performed, use `extraConfig.remap` instead.

`extraConfig` (attribute set) {#tester-lycheeLinkCheck-param-extraConfig}

: Extra configuration to pass to `lychee` in its [configuration file](https://github.com/lycheeverse/lychee/blob/master/lychee.example.toml).
  It is automatically [translated](https://nixos.org/manual/nixos/stable/index.html#sec-settings-nix-representable) to TOML.

  Example: `{ "include_verbatim" = true; }`

`lychee` (derivation, optional) {#tester-lycheeLinkCheck-param-lychee}

: The `lychee` package to use.

## `shellcheck` {#tester-shellcheck}

Run files through `shellcheck`, a static analysis tool for shell scripts, failing if there are any issues.

:::{.example #ex-shellcheck}
# Run `testers.shellcheck`

A single script

```nix
testers.shellcheck {
  name = "script";
  src = ./script.sh;
}
```

Multiple files

```nix
let
  inherit (lib) fileset;
in
testers.shellcheck {
  name = "nixbsd-activate";
  src = fileset.toSource {
    root = ./.;
    fileset = fileset.unions [
      ./lib.sh
      ./nixbsd-activate
    ];
  };
}
```

:::

### Inputs {#tester-shellcheck-inputs}

`name` (string, optional)
: The name of the test.
  `name` will be required at a future point because it massively improves traceability of test failures, but is kept optional for now to avoid breaking existing usages.
  Defaults to `run-shellcheck`.
  The name of the derivation produced by the tester is `shellcheck-${name}` when `name` is supplied.

`src` (path-like)
: The path to the shell script(s) to check.
  This can be a single file or a directory containing shell files.
  All files in `src` will be checked, so you may want to provide `fileset`-based source instead of a whole directory.

### Return value {#tester-shellcheck-return}

A derivation that runs `shellcheck` on the given script(s), producing an empty output if no issues are found.
The build will fail if `shellcheck` finds any issues.

## `shfmt` {#tester-shfmt}

Run files through `shfmt`, a shell script formatter, failing if any files are reformatted.

:::{.example #ex-shfmt}
# Run `testers.shfmt`

A single script

```nix
testers.shfmt {
  name = "script";
  src = ./script.sh;
}
```

Multiple files

```nix
let
  inherit (lib) fileset;
in
testers.shfmt {
  name = "nixbsd";
  src = fileset.toSource {
    root = ./.;
    fileset = fileset.unions [
      ./lib.sh
      ./nixbsd-activate
    ];
  };
}
```

:::

### Inputs {#tester-shfmt-inputs}