Bootstrap TypeError modal is not a function

Question

When I call  bootstrap modal from jquery I get this error:

TypeError: $(...).modal is not a function

My code :

<button id="btnTest" class="btn btn-default">Show Modal</button>
<div id="dummyModal" role="dialog" class="modal fade">
    <div class="modal-dialog">
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" data-dismiss="modal" class="close">&times;</button>
          <h4 class="modal-title">Error</h4>
        </div>
        <div class="modal-body">
          <p>Quick Brown Fox Jumps Over The Lazy Dog</p>
        </div>
        <div class="modal-footer">
          <button type="button" data-dismiss="modal" class="btn btn-default">Close</button>
        </div>
      </div>
    </div>
  </div>
</div>
<script type="text/javascript" src="/js/jquery-1.11.3.js"></script>
<script type="text/javascript" src="/js/bootstrap.js"></script>
<script type="text/javascript">
  $('document').ready(function () {
    $('#btnTest').click(function () {
        $('#dummyModal').modal('show');
    });
  });
</script>

Can someone help me to bypass this issue?