How can I see normal print output created during pytest run?

python

pytest

testing

debugging

byAlex Kataev·Feb 10, 2025

Activate immediate output during pytest by adding -s. This disables output capturing, allowing print() statements to be immediately visible.

Command:

pytest -s your_test_file.py

Usage in Test:

def test_sample():
    print("This will be printed during the test")
    assert 1 == 1  # Asserting the undeniable truths of life. Who needs philosophy?

Digging Deeper: Additional pytest output options

Outside the exemplary -s switch, pytest offers you a bunch of knives to tailor your output viewing experience:

pytest -rP to show input from tests that passed like a breeze
pytest -rx for the ones that hit the wall of failure
pytest --capture=tee-sys, for brilliant fellows with pytest v5.4.0 and onwards: logs stdout/stderr and keeps it in the console.

Remember to be skeptical about plugins, such as pytest-runner. It might feel tempting, but sticking to pytest's native features ensures stability.

Troubleshooting: When output capture doesn't behave

Issues with capturing? Check your imports and pytest environment.

Order-impaired imports breed runtime issues: Import pytest before _pytest. Monkey-patching PyTest.run_tests()? Be extra careful as stdout could be deceptive. Consider teeing stdout and stderr together for a panoramic view of the output.

A smart cookie would regularly check the pytest changelog and documentation to dodge quirks and bugs. Foresight saves the day!

Live on Stage: Output in PyCharm

PyCharm fans can rejoice with -s, as it's a wit to in-IDE debugging. It brings life to stdout during test execution. It's as simple as attaching -s in PyCharm's Run/Debug Configurations. Voila! Prints galore in the output console.

Experimenting: Exploring other capture methods

You can tap into the magic of the -r flag. It gives you a summary based on the results:

-ra: Unsilence all prints: revel in the details
-rf: It's a no-brainer: eyes on the failed tests.

Keep the testing pot boiling: Try custom fixtures that reel in capsys or capfd for more control. They let the print capture thrive even after the test. It's like an instant replay in slow motion!