Python: Mocking a context manager

Question

I don\'t understand why I can\'t mock NamedTemporaryFile.name in this example:

from mock import Mock, patch
import unittest
import tempfile

def myfunc():
           


        

Answer 1

Extending Peter K's answer using pytest and the mocker fixture.

def myfunc():
    with tempfile.NamedTemporaryFile(prefix='fileprefix') as fh:
        return fh.name


def test_myfunc(mocker):
    mocker.patch('tempfile.NamedTemporaryFile').return_value.__enter__.return_value.name = 'tempfilename'
    assert myfunc() == 'tempfilename'