nox session doesn't find pytest installed by poetry

I’m following along the Hypermodern Python series and it seems in Chapter 2, Test automation with Nox there is a conflict between nox and poetry. Specifically when I use the example noxfile.py:

import nox

@nox.session(python=["3.8", "3.7"])
def tests(session):
    session.run("poetry", "install", external=True)
    session.run("pytest", "--cov")

I get the following error:

nox > Running session tests-3.8
nox > Creating virtual environment (virtualenv) using python3.8 in .nox/tests-3-8
nox > poetry install
Installing dependencies from lock file

No dependencies to install or update

  - Installing testpkg (0.1.0)
nox > Program pytest not found.
nox > Session tests-3.8 failed.

(and the same for tests-3.7)

It seems that installing pytest via poetry as a dev dependency doesn’t put it on the path. In the previous section of Chapter 2, pytest was invoked through poetry and this does work in the nox session as well:

session.run('poetry', 'run', 'pytest', '--cov')

Is this an issue with my setup or is it expected that pytest can’t be run as a command when installed by poetry?

[joezilla86]

Your question helped me find the problem. The nox version was 2019.5.30 which did not match what my other computer was using. I ended up actually reinstalling my Ubuntu instance (running as WSL on Windows 10) and have been worked through the same initialization steps again. I realized that the installation of nox didn’t quite work as expected. Running “pip install --user --upgrade nox” did complete the install, but then the nox keyword would return

Command 'nox' not found, but can be installed with:
sudo apt install nox

So I realized I had installed via sudo which installed the 2019.5.30 version. The underlying issue is that using the pip method to install nox did not add it to PATH, so I just needed to add

export PATH="$HOME/.local/bin:$PATH" 

to my .bashrc file and reload the shell. Now it seems to work as expected.

[Dominik1123]

I created a corresponding issue.