nixos/auto-cpufreq: init vm test

Even though cpufreq cannot be adjusted within qemu this test is still
useful to ensure that the service is running and the auto-cpufreq cli is
able to interact with the auto-cpufreq service.

nixos/tests/all-tests.nix

@@ -141,6 +141,7 @@ in {
   audiobookshelf = handleTest ./audiobookshelf.nix {};
   auth-mysql = handleTest ./auth-mysql.nix {};
   authelia = handleTest ./authelia.nix {};
+  auto-cpufreq = handleTest ./auto-cpufreq.nix {};
   avahi = handleTest ./avahi.nix {};
   avahi-with-resolved = handleTest ./avahi.nix { networkd = true; };
   ayatana-indicators = runTest ./ayatana-indicators.nix;

nixos/tests/auto-cpufreq.nix

@@ -0,0 +1,33 @@
+import ./make-test-python.nix (
+  { pkgs, ... }:
+
+  {
+    name = "auto-cpufreq-server";
+
+    nodes = {
+      machine =
+        { pkgs, ... }:
+        {
+          # service will still start but since vm inside qemu cpufreq adjustments
+          # cannot be made. This will resource in the following error but the service
+          # remains up:
+          #   ERROR:
+          #   Couldn't find any of the necessary scaling governors.
+          services.auto-cpufreq = {
+            enable = true;
+            settings = {
+              charger = {
+                turbo = "auto";
+              };
+            };
+          };
+        };
+    };
+
+    testScript = ''
+      machine.start()
+      machine.wait_for_unit("auto-cpufreq.service")
+      machine.succeed("auto-cpufreq --force reset")
+    '';
+  }
+)