arekfu
commented
2 months ago I'm experiencing the same problem with output written directly by a C++ extension module to stdout. For some reason, Jupyter captures it in the cell output, but pytest-notebook does not.
I am not sure if this is intended behavior or a bug of the pytest+pytest-notebook combination, but it behaves different to JupyterLab (3.2.2): If a notebook runs a python function with multiprocessing in parallel and this python function emits messages to stdout via simple print() calls, typically, this output goes to the output of the respective notebook cell.
When running pytest over the notebook, it fails because the new cell output misses the print() messages and thus mismatches the stored notebook which contains the print() messages in its outputs.
Source repo with notebook
(Make sure to clone it recursively as it contains subrepos) The function being run with multiprocessing.subprocess(stdout=PIPE) on line 159 calls an external binary, captures its stderr and prints the captured stderr on stdout with print() finally. This print() messages do not get stored in the cell outputs during test runs (but they do with JupyterLab).
Thanks for any insights on this!
A recording of my pytest run:
(The ordering of the second batch of messages below differs, but nevertheless, it should be shown prefixed with '+' for 'obtained', right?)