ImportError: cannot import name 'transfer_markers' when testing with pytest

Question

When I run tests for my python project by running the following command:

python setup.py test
(or)
pytest project_name

I get the following error:

.../project_name/.eggs/pytest_asyncio-0.9.0-py3.6.egg/pytest_asyncio/plugin.py", line 8, in <module>
from _pytest.python import transfer_markers

ImportError: cannot import name 'transfer_markers'

Answer 1

When I looked it up online, there was almost no mention of that particular error message anywhere. Something similar has happened to me a few times before where previously working code just breaks and it's usually because there's a new version of an important package.

I looked at the pytest release history , and it looks like pytest==4.1.0 has been released a few hours ago (as of this post).

The solution is to revert back to the last stable version of pytest ie pytest==4.0.2 by running the following command:

pip install pytest==4.0.2

The tests are running now.

Answer 2

pytest-asyncio has been updated to 0.10.0

pytest-asyncio is using transfer_markers which is taken out in pytest 4.1.0. Looks like it's fixed and released. Issue #105

EDIT: You can now upgrade pip install pytest-asyncio==0.10.0 to fix this issue.

Or update pytest-asyncio==0.10.0 in your requirements.txt

Don't forget to run pip uninstall pytest to keep your pytest up-to-date if you previously installed pytest 4.0.2 to temporarily fix the issue