How to mock in pytest global variable in imported module?

[ryohei1540]

I have a module with methods, that I want to test with pytest. In my module I set up global vars such as logger. to use them in various places.

lib/sample.py

from google.cloud import logging

client = logging.Client()

class Sample:
    def __init__(self):
        ...

tests/sample_test.py

from lib.sample import Sample

@mock.patch.object(Sample, "bar", return_value=None)
def test_foo():
    ...

I got this error when I run pytest:

unit/lib/sample_test.py:X: in <module>
    from lib.sample import Sample
../lib/samlple.py:X: in <module>
    client = logging.Client()
../../../../X/lib/python3.7/site-packages/google/cloud/logging_v2/client.py:122: in __init__
    client_options=client_options,
../../../../X/lib/python3.7/site-packages/google/cloud/client.py:277: in __init__
    _ClientProjectMixin.__init__(self, project=project, credentials=credentials)
../../../../X/lib/python3.7/site-packages/google/cloud/client.py:225: in __init__
    project = self._determine_default(project)
../../../../X/lib/python3.7/site-packages/google/cloud/client.py:244: in _determine_default
    return _determine_default_project(project)
../../../../X/lib/python3.7/site-packages/google/cloud/_helpers.py:186: in _determine_default_project
    _, project = google.auth.default()
../../../../X/lib/python3.7/site-packages/google/auth/_default.py:356: in default
    raise exceptions.DefaultCredentialsError(_HELP_MESSAGE)
E   google.auth.exceptions.DefaultCredentialsError: Could not automatically determine credentials. Please set GOOGLE_APPLICATION_CREDENTIALS or explicitly create credentials and re-run the application. For more information, please see https://cloud.google.com/docs/authentication/getting-started```

I should not solve this error to set the variable as a prerequisite to use this code for members.

How can I mock or patch any module or function?

[nicoddemus]

Hi @ryohei1540,

It is not clear why this is related to pytest. Seems that creating client = logging.Client() when importing lib/sample.py is blowing up due to missing credentials.

What happens if you execute python -c "import lib.sample"?