How to mock global modules

So, imagine if you want to mock an external dependency in a script, like this one that is connection to AWS

# script.py
import boto3

client = boto3.client("ssm")

If you follow python documentation and apply for this case, will not work. For this case, you need to mock the module itself.

Unfortunately, I wasn’t able to mock boto3 entirely, but I can mock the client(), this way:

# test.py
from unittest.mock import patch

@patch("boto3.client")
def test_boto(boto3):
    import script
    assert isinstance(script.client, MagicMock)
    

And done :)