Flask app wrapped with DispatcherMiddleware no longer has test_client
<p>We can obtain <code>test_client</code> for sample application in way like: </p>

<pre><code>class MyTestCase(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        my_app.app.config['TESTING'] = True
        cls.client = my_app.app.test_client()
</code></pre>

<p>However, if we wrap app with <code>DispatcherMiddleware</code> - we will get error like
 <code>AttributeError: 'DispatcherMiddleware' object has no attribute 'test_client'</code>.</p>

<p>Are there way to test composition of flask applications? </p>

<p>We want to be able to do something like: </p>

<pre><code>cls.client = my_app.all_apps.test_client()
</code></pre>

<p>When <code>all_apps</code> is middleware like: </p>

<pre><code>all_apps = DispatcherMiddleware(my_app, {
    '/backend': backend_app,
})
</code></pre>