To run pytest we can setup a custom hook by providing the local repo. This allows us to basically define whatever we want. The setup needs a few keys.

id, name and language are self explanatory

entry defines the scrip that needs to be run. In our case pytest located in the virtual environment. A caveat is that this assumes that everyone working on the project has the same venv location.

pass_filenames is set to true since we don't want pre-commit to pass any filenames to the hook, that'd make pytest crash

always_run is set to true to ensure the tests always run, even when there are no files staged

repos:  
  - ...
  - ...
  - ...
  - repo: local  
    hooks:  
      - id: pytest  
        name: pytest  
        entry: ./.venv/bin/pytest tests  
        language: python  
        pass_filenames: false  
        always_run: true