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Comment by BiteCode_dev | Hacker News Reader

What's the benefit of doing this instead of just using the watchmedo command from watchdog directly ?

    watchmedo shell-command --patterns="*.py" --ignore-directories --recursive . -c "pytest"

As a bonus, watchmedo works for your server, your bundler, you task queue process, etc.

It seems that there is no need to create one tool per command you wish to run. Or am I missing something? Do you only reload tests that are related to the code change?

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First, I think for many users typing:

  ptw .

is a lot simpler than typing:

  watchmedo shell-command --patterns="\*.py" --ignore-directories --recursive . -c "pytest"

Second, I personally faced problems with suggested approach. I use neovim with ale plugin that automatically formats my code with black every time I save python file. That's two saves instead of one. In that case watchmedo will trigger pytest to run twice, which is usually not the desired behavior. Sometimes you also just save your file multiple times quickly and you want pytest to run only once with latest changes in mind.

In my tool, there is a 0.5 seconds delay (configurable --delay). pytest-watcher will wait this time for other changes before starting pytest.

Regarding running tests for changed code only, there is a pytest-testmon plugin which does exactly that. It can be used together with pytest-watcher. Here is the link:

https://testmon.org/

> that case watchmedo will trigger pytest to run twice,

That's what the --drop options is for. It's better than delay, since it drops any event while the command is running, no matter the time it took.

> First, I think for many users typing: ... is a lot simpler than typing:...

I think somebody using pytest is perfectly capable of doing:

alias ptw='watchmedo shell-command --patterns="*.py" --ignore-directories --recursive . -c "pytest" --drop'

Or putting that in a makefile, a dodo.py file or what have you.

I don’t think that —drop is better than delay in case of tests. Quite contrary, one usually wants them to run after latest save not the first one.

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