nixos/systemd-boot: Add basic test

nixos/modules/virtualisation/qemu-vm.nix

@@ -189,9 +189,18 @@ let
           mkdir /boot/grub
           echo '(hd0) /dev/vda' > /boot/grub/device.map
 
-          # Install GRUB and generate the GRUB boot menu.
-          touch /etc/NIXOS
+          # This is needed for systemd-boot to find ESP, and udev is not available here to create this
+          mkdir -p /dev/block
+          ln -s /dev/vda2 /dev/block/254:2
+
+          # Set up system profile (normally done by nixos-rebuild / nix-env --set)
           mkdir -p /nix/var/nix/profiles
+          ln -s ${config.system.build.toplevel} /nix/var/nix/profiles/system-1-link
+          ln -s /nix/var/nix/profiles/system-1-link /nix/var/nix/profiles/system
+
+          # Install bootloader
+          touch /etc/NIXOS
+          export NIXOS_INSTALL_BOOTLOADER=1
           ${config.system.build.toplevel}/bin/switch-to-configuration boot
 
           umount /boot

nixos/tests/all-tests.nix

@@ -297,6 +297,7 @@ in
   syncthing-relay = handleTest ./syncthing-relay.nix {};
   systemd = handleTest ./systemd.nix {};
   systemd-analyze = handleTest ./systemd-analyze.nix {};
+  systemd-boot = handleTestOn ["x86_64-linux"] ./systemd-boot.nix {};
   systemd-confinement = handleTest ./systemd-confinement.nix {};
   systemd-timesyncd = handleTest ./systemd-timesyncd.nix {};
   systemd-networkd-vrf = handleTest ./systemd-networkd-vrf.nix {};

nixos/tests/systemd-boot.nix

@@ -0,0 +1,31 @@
+{ system ? builtins.currentSystem,
+  config ? {},
+  pkgs ? import ../.. { inherit system config; }
+}:
+
+with import ../lib/testing-python.nix { inherit system pkgs; };
+with pkgs.lib;
+
+makeTest {
+  name = "systemd-boot";
+  meta.maintainers = with pkgs.stdenv.lib.maintainers; [ danielfullmer ];
+
+  machine = { pkgs, lib, ... }: {
+    virtualisation.useBootLoader = true;
+    virtualisation.useEFIBoot = true;
+    boot.loader.systemd-boot.enable = true;
+  };
+
+  testScript = ''
+    machine.start()
+    machine.wait_for_unit("multi-user.target")
+
+    machine.succeed("test -e /boot/loader/entries/nixos-generation-1.conf")
+
+    # Ensure we actually booted using systemd-boot.
+    # Magic number is the vendor UUID used by systemd-boot.
+    machine.succeed(
+        "test -e /sys/firmware/efi/efivars/LoaderEntrySelected-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"
+    )
+  '';
+}