diff --git a/website/README.md b/website/README.md
index 7944591..bc5ac99 100644
--- a/website/README.md
+++ b/website/README.md
@@ -30,6 +30,26 @@ Structured content is managed through Nix expressions, and copy is written in [C
 
 - Edit any of the files, see [repository layout](#repository-layout) for guidance
 
+# Testing
+
+As a derivation, e.g. for CI:
+
+```bash
+nix-build -A tests
+```
+
+In the development shell:
+
+```bash
+run-tests
+```
+
+Running tests in a loop on source code changes:
+
+```bash
+test-loop
+```
+
 # Repository layout
 
 - [content](./content)
diff --git a/website/default.nix b/website/default.nix
index b8a99f4..dc4c662 100644
--- a/website/default.nix
+++ b/website/default.nix
@@ -14,12 +14,7 @@ let
     in
     new // { types = prev.recursiveUpdate prev.types new.types; };
   lib'' = lib.extend lib';
-  # TODO: update when the PR to expose `pkgs.devmode` is merged
-  #       https://github.com/NixOS/nixpkgs/pull/354556
-  devmode = pkgs.callPackage "${sources.devmode-reusable}/pkgs/by-name/de/devmode/package.nix" {
-    buildArgs = "${toString ./.} -A build --show-trace";
-    open = "/index.html";
-  };
+
 in
 rec {
   lib = lib'';
@@ -38,11 +33,36 @@ rec {
 
   inherit (result.config) build;
 
-  shell = pkgs.mkShellNoCC {
-    packages = with pkgs; [
-      cmark
-      npins
-      devmode
-    ];
-  };
+  shell =
+    let
+      run-tests = pkgs.writeShellApplication {
+        name = "run-tests";
+        text = with pkgs; with lib; ''
+          ${getExe nix-unit} ${toString ./tests.nix} "$@"
+        '';
+      };
+      test-loop = pkgs.writeShellApplication {
+        name = "test-loop";
+        text = with pkgs; with lib; ''
+          ${getExe watchexec} -w ${toString ./.} -- ${getExe nix-unit} ${toString ./tests.nix}
+        '';
+      };
+      devmode = pkgs.devmode.override {
+        buildArgs = "${toString ./.} -A build --show-trace";
+        open = "/index.html";
+      };
+    in
+    pkgs.mkShellNoCC {
+      packages = [
+        pkgs.npins
+        run-tests
+        test-loop
+        devmode
+      ];
+    };
+
+  tests = with pkgs; with lib; runCommand "run-tests" { } ''
+    touch $out
+    ${getExe nix-unit} ${./tests.nix} "$@"
+  '';
 }
diff --git a/website/lib.nix b/website/lib.nix
index 4b6ea34..6dcff3a 100644
--- a/website/lib.nix
+++ b/website/lib.nix
@@ -104,7 +104,7 @@ rec {
       path1 = subpath.components path1';
       prefix1 = with lib; take (length path1 - 1) path1;
       path2 = subpath.components path2';
-      prefix2 = with lib; take (length path1 - 1) path2;
+      prefix2 = with lib; take (length path2 - 1) path2;
 
       commonPrefixLength = with lists;
         findFirstIndex (i: i.fst != i.snd)
diff --git a/website/npins/sources.json b/website/npins/sources.json
index ebb34b2..37368b4 100644
--- a/website/npins/sources.json
+++ b/website/npins/sources.json
@@ -1,22 +1,22 @@
 {
   "pins": {
-    "devmode-reusable": {
+    "nix-unit": {
       "type": "Git",
       "repository": {
         "type": "GitHub",
-        "owner": "fricklerhandwerk",
-        "repo": "nixpkgs"
+        "owner": "nix-community",
+        "repo": "nix-unit"
       },
-      "branch": "refactor-devmode",
-      "revision": "f0746a6690939987734d6519a2e3daf28ed36d87",
-      "url": "https://github.com/fricklerhandwerk/nixpkgs/archive/f0746a6690939987734d6519a2e3daf28ed36d87.tar.gz",
-      "hash": "011kg3c2mfy7y808llpmq3hf6vv6rlazx8m11w41pnym4kwr3ivz"
+      "branch": "main",
+      "revision": "2071bbb765681ac3d8194ec560c8b27ff2a3b541",
+      "url": "https://github.com/nix-community/nix-unit/archive/2071bbb765681ac3d8194ec560c8b27ff2a3b541.tar.gz",
+      "hash": "0blz1kcmn9vnr9q3iqp2mv13hv3pdccljmmc54f8j7ybf5v0wgmp"
     },
     "nixpkgs": {
       "type": "Channel",
       "name": "nixpkgs-unstable",
-      "url": "https://releases.nixos.org/nixpkgs/nixpkgs-24.11pre691017.b69de56fac8c/nixexprs.tar.xz",
-      "hash": "0z32pj0lh5ng2a6cn0qfmka8cynnygckn5615mkaxq2aplkvgzx3"
+      "url": "https://releases.nixos.org/nixpkgs/nixpkgs-25.05pre711046.8edf06bea5bc/nixexprs.tar.xz",
+      "hash": "1mwsn0rvfm603svrq3pca4c51zlix5gkyr4gl6pxhhq3q6xs5s8y"
     }
   },
   "version": 3
diff --git a/website/tests.nix b/website/tests.nix
new file mode 100644
index 0000000..5fe31b6
--- /dev/null
+++ b/website/tests.nix
@@ -0,0 +1,11 @@
+# tests written for running with `nix-unit`
+# https://github.com/nix-community/nix-unit
+let
+  inherit (import ./. { }) lib;
+in
+{
+  test-relativePath = {
+    expr = with lib; relativePath "bar" "baz";
+    expected = "./baz";
+  };
+}