How to assert output with nosetest/unittest in python?

Question

I\'m writing tests for a function like next one:

def foo():
    print \'hello world!\'

So when I want to test this function the code will b

Answer 1

A lot of these answers failed for me because you can't from StringIO import StringIO in Python 3. Here's a minimum working snippet based on @naxa's comment and the Python Cookbook.

from io import StringIO
from unittest.mock import patch

with patch('sys.stdout', new=StringIO()) as fakeOutput:
    print('hello world')
    self.assertEqual(fakeOutput.getvalue().strip(), 'hello world')