javascript - jQuery: Simple plugin does not work -

i trying create plugin jquery. basic plugin (plugin.js)

(function ( $ ) {  $.fn.testplugin= function() {    alert('test');  }( jquery )); 

this file (ext.js) calls function testplugin() inside plugin.js

$(document).ready(function(){  $('p').testplugin();  }; 

in html page included files above plus jquery library (jquery.js)

<script type="text/javascript" src="js/jquery.js"></script> <script type="text/javascript" src="js/plugin.js"></script> <script type="text/javascript" src="js/ext.js"></script> 

unfortunately plugin not work expected.

well, simple example work (after removed ) mentioned tibzon , wojtek).

$.fn.testplugin=function(){ alert('test'); };    $('p').testplugin()

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

i left out enclosing parenthetical expression (function($){ ... })(jquery) doesn't make difference example chosen. variable affected $ itself.