Vue 使用时警告未声明？app.js 里的 Vue 怎么使用？

app.blade.php文件中

        <div id="testing">@{{testing}}</div>
<!-- Scripts -->
    <!-- <script type="text/javascript" src="{{asset('js/vue.js')}}"></script> -->
    <script src="{{ asset('js/app.js') }}"></script>
    <script type="text/javascript">
        new Vue({
            el:'#testing',
            data:{
                testing:'12345'
            }
        });
    </script>

报错

[Vue warn]: Property or method "testing" is not defined on the instance but referenced during render. Make sure to declare reactive data properties in the data option.

但是我如果注释掉app.js，用vue.js就可以，app.js里面的Vue如何使用呢？