uselazy_static::lazy_static;usestd::sync::Mutex;lazy_static!{pubstaticrefTEST_MUTEX:Mutex<()>=Mutex::new(());}/// There can only be one thread running at the time with a QQuickEngine
/// (in principle, everything should be in the same main thread)
pubfnlock_for_test()->std::sync::MutexGuard<'static, ()>{TEST_MUTEX.lock().unwrap_or_else(|e|e.into_inner())}