Run Python test suites without leaving Emacs

Recently, I'm trying to overcome my laziness and incorporate more automated testing into my software development procedure. It's not that I wasn't developing test suites before, but the problem was that the overall process of defining good tests, running and maintaining them was so complicated to me which most of the time was pushing me to prefer not to test until I have enough time to work on it (which of course was never in real life).

Trying to achieve better quality in the code I write, I learned that the problem is not caused by the process itself, but it’s usually either caused by my designs or my lack of experience. And all of that was blocking me to achieve all of the promised TDD's benefits.

So, now I'm practicing to resolve my problems (either in design or in workflow) and one of the first things I needed was something to help me to run the test suite without leaving my editor.

A quick search and I found the emacs-python-pytest package for Emacs. It's not the only implementation of course. But what I like about this package, is that it uses Magit popup to help users with finding the proper options they want to have in the pytest call. This feature was very helpful for me with git commands, so I don't need to remember all the weird argument combination; I hope it'll help me with pytest as well ;-)

Here is the configuration I used to enable this package:

(use-package python-pytest
  :after python
  :custom
  (python-pytest-arguments
   '("--color"          ;; colored output in the buffer
     "--failed-first"   ;; run the previous failed tests first
     "--maxfail=5"))    ;; exit in 5 continuous failures in a run
  :config
  (which-key-declare-prefixes-for-mode 'python-mode "SPC pt" "Testing")
  (evil-leader/set-key-for-mode 'python-mode
    "ptp" 'python-pytest-popup
    "ptt" 'python-pytest
    "ptf" 'python-pytest-file
    "ptF" 'python-pytest-file-dwim
    "ptm" 'python-pytest-function
    "ptM" 'python-pytest-function-dwim
    "ptl" 'python-pytest-last-failed)
  )

There isn't much to describe this configuration, and as you see it's heavily dependent on other parts of my Emacs configuration. But I guess the features available are self-explanatory. So now, whenever I want to run the full test suite, I'll type <SPC> ptt. However the most useful keybinding I have here is the <SPC> ptm which runs the current test function, so I can focus exactly on one test at a time.

Using the <SPC> ptp command I can access to the pytest popup menu where I have options to for example run pytest with a debugger (pdb) invoked on failures 😋.

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