test(services): run tests during system builds

common/optional/zfs/snapshot.nix

@@ -1,4 +1,5 @@
 {
+  inputs,
   pkgs,
   lib,
   config,
@@ -6,6 +7,11 @@
 }:
 let
   cfg = config.services.snapshot_manager;
+  snapshotManagerPackages =
+    ps: with ps; [
+      apprise
+      typer
+    ];
 in
 {
   options = {
@@ -36,15 +42,39 @@ in
   config = lib.mkIf cfg.enable {
     nixpkgs.overlays = [
       (final: _prev: {
-        snapshot_manager_python = final.python314.withPackages (
-          ps: with ps; [
-            apprise
-            typer
-          ]
+        snapshot_manager_python = final.python314.withPackages snapshotManagerPackages;
+        snapshot_manager_test_python = final.python314.withPackages (
+          ps:
+          snapshotManagerPackages ps
+          ++ (with ps; [
+            pyfakefs
+            pytest
+            pytest-asyncio
+            pytest-mock
+            pytest-xdist
+          ])
         );
+        snapshot_manager_tests =
+          final.runCommand "snapshot-manager-tests"
+            {
+              nativeBuildInputs = [ final.snapshot_manager_test_python ];
+            }
+            ''
+              export HOME="$TMPDIR"
+              cd ${inputs.self}
+              pytest \
+                -o cache_dir="$TMPDIR/pytest-cache" \
+                tests/test_common.py \
+                tests/test_signal_alert.py \
+                tests/test_snapshot_manager.py \
+                tests/test_zfs.py
+              touch "$out"
+            '';
       })
     ];
 
+    system.checks = [ pkgs.snapshot_manager_tests ];
+
     systemd = {
       services.snapshot_manager = {
         description = "ZFS Snapshot Manager";