Python Testing with pytest

Using recwarn

The recwarn builtin fixture is used to examine warnings generated by code under test. In Python, you can add warnings that work a lot like assertions, but are used for things that don’t need to stop execution. For example, suppose we want to stop supporting a function that we wish we had never put into a package but was released for others to use. We can put a warning in the code and leave it there for a release or two:

ch4/test_warnings.py

import warnings
import pytest


def lame_function():
    warnings.warn("Please stop using this", DeprecationWarning)
    # rest of function

We can make sure the warning is getting issued correctly with a test:

ch4/test_warnings.py

def test_lame_function(recwarn):
 lame_function() ...