Testing a Jupyter Notebook - testing

Question

I am trying to come up with a method to test a number of Jupyter notebooks. A test should run when a new notebook is implemented in a Github branch and submitted for a pull request. The tests are not that complicated, they are mostly just testing if the notebook runs end-to-end and without any errors, and maybe a few asserts. However:
There are certain calls in some cells that need to be mocked, e.g. a call to download the data from a database.
There may be some magic cells in the notebooks which run a pip command or something else.
I am open to use any testing library, such as 'pytest' or unittest, although pytest is preferred.
I looked at a few libraries for testing notebooks such as nbmake, treon, and testbook, but I was unable to make them work. I also tried to convert the notebook to a python file, but the magic cells were converted to a get_ipython().run_cell_magic(...) call which became an issue, since pytest uses python and not ipython, and get_ipython() is only available in ipython.
So, I am wondering what is a good way to test jupyter notebooks with all of that in mind. Any help is appreciated.

Answer 1

One straightforward approach I've already used is to execute the entire notebook with nbconvert.
A notebook failed.ipynb raising an exception will result in a failed run thanks to the --execute option that tells nbconvert to execute the notebook prior to its conversion.
jupyter nbconvert --to notebook --execute failed.ipynb
# ...
# Exception: FAILED
echo $?
# 1
Another correct notebook passed.ipynb will result in a successful export.
jupyter nbconvert --to notebook --execute passed.ipynb
# [NbConvertApp] Converting notebook passed.ipynb to notebook
# [NbConvertApp] Writing 1172 bytes to passed.nbconvert.ipynb
echo $?
# 0
Cherry on the cake, you can do the same through the API and so wrap it in Pytest!
import nbformat
import pytest
from nbconvert.preprocessors import ExecutePreprocessor
#pytest.mark.parametrize("notebook", ["passed.ipynb", "failed.ipynb"])
def test_notebook_exec(notebook):
with open(notebook) as f:
nb = nbformat.read(f, as_version=4)
ep = ExecutePreprocessor(timeout=600, kernel_name='python3')
try:
assert ep.preprocess(nb) is not None, f"Got empty notebook for {notebook}"
except Exception:
assert False, f"Failed executing {notebook}"
Running the test gives.
pytest test_nbconv.py
# FAILED test_nbconv.py::test_notebook_exec[failed.ipynb] - AssertionError: Failed executing failed.ipynb
# PASSED test_nbconv.py::test_notebook_exec[passed.ipynb]
Notes
There is several output formats, I've used here notebook.
This doesn’t convert a notebook to a different format per se, instead it allows the running of nbconvert preprocessors on a notebook, and/or conversion to other notebook formats.
The python code example is just a quick draft it can be largely improved.

Answer 2

Here is my own solution using testbook. Let's say I have a notebook called my_notebook.ipynb with the following content:
The trick is to inject a cell before my call to bigquery.Client and mock it:
from testbook import testbook
#testbook('./my_notebook.ipynb')
def test_get_details(tb):
tb.inject(
"""
import mock
mock_client = mock.MagicMock()
mock_df = pd.DataFrame()
mock_df['week'] = range(10)
mock_df['count'] = 5
p1 = mock.patch.object(bigquery, 'Client', return_value=mock_client)
mock_client.query().result().to_dataframe.return_value = mock_df
p1.start()
""",
before=2,
run=False
)
tb.execute()
dataframe = tb.get('dataframe')
assert dataframe.shape == (10, 2)
x = tb.get('x')
assert x == 7