unit testing - Python mock patch doesn't work as expected for public method

Question

I'm trying to patch a public method for my flask application but it doesn't seem to work.

Here's my code in mrss.feed_burner

def get_feed(env=os.environ):
   return 'something'

And this is how I use it

@app.route("/feed")
    def feed():
        mrss_feed = get_feed(env=os.environ)
        response = make_response(mrss_feed)
        response.headers["Content-Type"] = "application/xml"

        return response

And this is my test which it's not parsing.

def test_feed(self):
    with patch('mrss.feed_burner.get_feed', new=lambda: '<xml></xml>'):
        response = self.app.get('/feed')
        self.assertEquals('<xml></xml>', response.data)

Answer 1

I believe your problem is that you're not patching in the right namespace. See where_to_patch documentation for unittest.mock.patch.

Essentially, you're patching the definition of get_feed() in mrss.feed_burner but your view handler feed() already has a reference to the original mrss.feed_burner.get_feed(). To solve this problem, you need to patch the reference in your view file.

Based on your usage of get_feed in your view function, I assume you're importing get_feed like so

view_file.py

from mrss.feed_burner import get_feed

If so, you should be patching view_file.get_feed like so:

def test_feed(self):
    with patch('view_file.get_feed', new=lambda: '<xml></xml>'):
        ...