Testing Single File Python Applications/Scripts with pytest and coverage

Episode 147 · March 5th, 2021 · 11 mins 24 secs

About this Episode

Have you ever written a single file Python application or script?
Have you written tests for it?
Do you check code coverage?

This is the topic of this weeks episode, spurred on by a listener question.

The questions:

  • For single file scripts, I'd like to have the test code included right there in the file. Can I do that with pytest?
  • If I can, can I use code coverage on it?

The example code discussed in the episode: script.py

def foo():
    return 5

def main():
    x = foo()

if __name__ == '__main__': # pragma: no cover

## test code

# To test:
# pip install pytest
# pytest script.py

# To test with coverage:
# put this file (script.py) in a directory by itself, say foo
# then from the parent directory of foo:
# pip install pytest-cov
# pytest --cov=foo foo/script.py

# To show missing lines
# pytest --cov=foo --cov-report=term-missing foo/script.py

def test_foo():
    assert foo() == 5

def test_main(capsys):
    captured = capsys.readouterr()
    assert captured.out == "5\n"

Suggestion by @cfbolz if you need to import pytest:

if __name__ == '__main__': # pragma: no cover
   import pytest

Full Transcript