Python MagicMock returns bytes value for HTTP response

Question

I want to mock HTTP request that returns an image (bytes) with MagicMock. So, I have simple function here:

import io
import urllib.request

def blah():
    try:
        req = urllib.request.Request(url='<image url/base64>', data=None, method='GET')
        response = urllib.request.urlopen(req)
    except Exception as e:
        return str(e)

    body = io.BytesIO(response.read())  # error here

    return 'something'

And I want test it, like this:

import unittest
from blah import blah
from unittest.mock import patch, MagicMock

class TestBlah(unittest.TestCase):
    def test_blah(self):
        with patch('urllib.request.urlopen') as mock_urlopen:
            cm = MagicMock()
            cm.getcode.return_value = 200
            cm.read.return_value = open('./download.jpeg')  # an image file
            cm.__enter__.return_value = cm
            mock_urlopen.return_value = cm

            self.assertEqual(blah(), 'something')

When I execute my code, it produces error:

TypeError: a bytes-like object is required, not '_io.TextIOWrapper'

Can anyone help me?

Answer 1

It should be like this,

cm.read.return_value = open('./download.jpeg', 'rb').read()