testing: save some common cli options

testing.nix

@@ -10,11 +10,18 @@ in
     ./configuration.nix
   ];
 
+  virtualisation.memorySize = "4000"; # MB
+
+  virtualisation.qemu.options = [
+    # Use serial console to access the VM
+    "-display none"
+    "-serial mon:stdio"
+
     # Ensure secrets are accessible by the
     # activation scripts at runtime.
-  virtualisation.qemu.options = [
     "-virtfs local,path=${secrets},security_model=none,mount_tag=secrets"
   ];
+
   fileSystems = lib.mkVMOverride {
    "${secrets}" =
       { device = "secrets";