public void Do_not_export_unexportable()
        {
            var canExport = false;

            shell.CanExport.Changed().Subscribe(_ => canExport = shell.CanExport.Value);
            var export = new ExportScreen();

            export.CanExport.Value = true;
            shell.ActivateItem(export);
            Assert.IsTrue(canExport);
            shell.ActivateItem(new Screen());
            Assert.IsFalse(canExport);
        }
        public void Track_can_export_changes()
        {
            var canExport = false;

            shell.CanExport.Changed().Subscribe(_ => canExport = shell.CanExport.Value);
            var export = new ExportScreen();

            shell.ActivateItem(export);

            export.CanExport.Value = true;

            Assert.IsTrue(canExport);
        }