Spec add "first run" test

spec/vncserver_spec.py

@@ -48,6 +48,15 @@ with description('vncserver') as self:
     with after.each:
         kill_xvnc()
 
+    with it('asks user to select a DE on the first run'):
+        add_kasmvnc_user_docker()
+
+        cmd = f'{vncserver_cmd}'
+        completed_process = run_cmd(cmd, input="1\ny\n")
+        expect(completed_process.returncode).to(equal(0))
+
+        check_de_was_setup_to_run('cinnamon')
+
     with it('selects passed DE with -s'):
         add_kasmvnc_user_docker()