Python mock patch doesn't work as expected for public method
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_feedIf 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>'): ...