nixos/switch-test: add test for multi-line unit values

nixos/tests/switch-test.nix

@@ -260,6 +260,15 @@ in {
           systemd.services."escaped\\x2ddash".serviceConfig.X-Test = "test";
         };
 
+        unitWithMultilineValue.configuration = {
+          systemd.services.test.serviceConfig.ExecStart = ''
+            ${pkgs.coreutils}/bin/true \
+            # ignored
+            ; ignored
+              blah blah
+          '';
+        };
+
         unitStartingWithDash.configuration = {
           systemd.services."-" = {
             wantedBy = [ "multi-user.target" ];
@@ -874,9 +883,16 @@ in {
         machine.succeed("! test -e /run/current-system/dry-activate")
         machine.succeed("! test -e /run/current-system/bin/switch-to-configuration")
 
+        # Ensure units with multiline values work
+        out = switch_to_specialisation("${machine}", "unitWithMultilineValue")
+        assert_lacks(out, "NOT restarting the following changed units:")
+        assert_lacks(out, "reloading the following units:")
+        assert_lacks(out, "restarting the following units:")
+        assert_lacks(out, "the following new units were started:")
+        assert_contains(out, "starting the following units: test.service")
+
         # Ensure \ works in unit names
         out = switch_to_specialisation("${machine}", "unitWithBackslash")
-        assert_contains(out, "stopping the following units: test.service\n")
         assert_lacks(out, "NOT restarting the following changed units:")
         assert_lacks(out, "reloading the following units:")
         assert_lacks(out, "\nrestarting the following units:")