Testing w Python, Pytest, Debugger & Virtual Environment in Visual Studio Code

So for awhile now I’ve been struggling to put this all together neatly. I’ve been using one command for testing and another for debugging my code. But today I finally put it all together and boy does it feel amazing!

So what not all my tests are passing lol. They are actually there in the tests tab!!! For so long I wondered what that thing was even for, or how it worked. Now I know!

And yes, now there’s this wonderful button that can run the test with a debugger. So I go and set a breakpoint, push the magic button, and boom my test runs correctly and pauses on my breakpoint for me to see what is going on. Wow, this feels great!

So how did I do this? Admittedly my solution was a bit of a hack. I first tried going through the settings, and googling some things, but I honestly could not find the happy easy path. I ultimately had to read the commands that Visual Studio Code (VSC) was trying to run and modify them a bit.

The nitty gritty:

An important piece to note, as this was confusing VSC: My project folder structure looks something like this

project_name/app/test/test_api

So I would have VSC open in the root folder, when I tried to use the Testing tab, I would set it up with “Pytest” as the testing framework, and then the folder for the tests would be “app”. It honestly would not allow me to choose a deeper folder than app. So after I clicked that button, nothing would happen.

So I eventually opened the /app folder in VSC like this:

code app

Now from this context, I was able to push those same buttons in the testing tab, but this time something happened as I was able to choose the “test/“ folder as the entry point for my tests. It seemed to pick those up, however there was still an error with it working correctly.

So I opened up the Output tab (Near the terminal tab) and started reading through. All my tests were failing because they could not find certain modules. I’ve seen this before so I recognized that this was an issue with the code not being ran from my Virtual Environment which has all my modules/packages set up. Still felt like progress.

So scrolling up on the Python Output page, I saw where the tests began to run, and I could see the command that VSC was using to try to set up the tests tab. It looked something like this:

~/.pyenv/versions/3.9.7/bin/python ~/.vscode/extensions/ms-python.python-2022.6.3/pythonFiles/testing_tools/run_adapter.py discover pytest -- --rootdir . -s --cache-clear test

Ok, very interesting. So I went back to my other VSC window which was opened at the root project folder. I opened a terminal and activated the Virtual Environment for this app. I got the location of the python file that runs inside that virtual environment with this command:

which python

It pointed to this python file

/Users/izzlenizzle/.pyenv/shims/python

I noticed that the code VSC was running was pointing to a different python file, so I figured I’d try just swapping out that python for the python file inside my virtual environment.

So notably I was back in my root folder directory VSC window, as this was where I wanted to configure the Tests tab ultimately. I then needed to modify the command in one other place in addition to the python path.

I also updated the path to the test folder. I noticed that at the end of the command I pulled from VSC, there was an argument for “test”. I recognized that was the path for my tests, so I just updated that to the path to my tests from the context of my root project directory. Here is the ultimate command I used:

/Users/izzlenizzle/.pyenv/shims/python ~/.vscode/extensions/ms-python.python-2022.6.3/pythonFiles/testing_tools/run_adapter.py discover pytest -- --rootdir . -s --cache-clear app/test

This ran and outputted a rather large JSON string to the terminal. It appeared to have some information regarding my tests and there locations. That gave me the impression that something happened. I then opened my VSC Tests tab and to my surprise I could see the tree of my tests there! 🎊🎉

This honestly came as a surprise because I’ve been digging for a solution for a long time now. I tried digging around in different settings and googling around, digging through Github issues and comments there. But I ultimately found this solution. Now I realize it’s tacky, but I’m perfectly satisfied with finding this as it really helps me increase my development speed and reduce bugs.

I understand that switching virtual environments inside this project would likely mean re-initializing the tests tab, and that’s not a great experience. But if that were your situation, I imagine using the previous command with the updated path for the python executable would do the trick.

But if anyone is aware of the better way of doing this, I am open to hear it! Feel free to DM me on twitter.

Hope this helps!