Mocking urllib.request.urlopen using unittest - request

Question

I'm trying to mock this urlopen function. Got a couple of solutions from other similar questions but none of them seems to work.
def lambda_handler(event, context):
try:
request = urllib.request.Request(url = URL, data = data, method = method, headers = headers)
with urllib.request.urlopen(request) as httpResponse:
# print(httpResponse.read().decode('utf-8'))
string = httpResponse.read().decode('utf-8')
response = json.loads(string)
print(response)
return response
Approach tried:
class mock_request():
class Request():
....
def urlopen(*args, **krwargs):
return {}
#mock.patch(.....urllib.request, mock_request)

Answer 1

I think the easiest way is to patch __enter__ + __exit__ methods. Just an example:
def lambda_handler(event, context):
try:
# some request... just an example
request = Request('https://restcountries.com/v3.1/name/belarus')
with urllib.request.urlopen(request) as resp:
string = resp.read().decode('utf-8')
return json.loads(string)
except Exception:
pass
Test:
from unittest import TestCase, mock
from unittest.mock import Mock
class TestExample(TestCase):
def test_lambda_handler(self):
print(lambda_handler(1, 2)) # real result from restcountries
open_mock = Mock(
# resp.read().decode('utf-8') will return static value '[]'
__enter__=Mock(return_value=Mock(read=Mock(return_value=Mock(decode=Mock(return_value='[]'))))),
__exit__=Mock(),
)
with mock.patch('urllib.request.urlopen', return_value=open_mock):
print(lambda_handler(1, 2)) # []
# resp.read().decode('utf-8') will return dynamic values
open_mock = Mock(
__enter__=Mock(
return_value=Mock(
read=Mock(return_value=Mock(decode=Mock(side_effect=[
'[{"name": "N S"}]',
'[{"name": "D G"}]']
)))
)
),
__exit__=Mock(),
)
with mock.patch('urllib.request.urlopen', return_value=open_mock):
print(lambda_handler(1, 2)) # [{"name": "N S"}]
print(lambda_handler(1, 2)) # [{"name": "D G"}]