pytest.approx fails with TypeError: unsupported operand type(s) for -: 'float' and 'NoneType' #10702
Description
When using approx to test float and one of the objects in the assert statement contain None I see the following TypeError:
TypeError: unsupported operand type(s) for -: 'float' and 'NoneType'.
Minimal example
Test
import pytest # Expecting assertion error with differing item # Instead I see "TypeError: unsupported operand type(s) for -: 'float' and 'NoneType'." def test_pytest_none_approx(): actual_result = {"a": 1.2} expected_result = {"a": None} approx_expected_result = pytest.approx(expected_result) assert approx_expected_result == actual_result Output
E AssertionError: assert approx({'a': 1.2 ± 1.2e-06}) == {'a': None} E (pytest_assertion plugin: representation of details failed: /Users/milanwiedemann/.pyenv/versions/3.10.4/lib/python3.10/site-packages/_pytest/python_api.py:270: TypeError: unsupported operand type(s) for -: 'float' and 'NoneType'. E Probably an object has a faulty __repr__.) pip list
Package Version -------------- ------- attrs 22.2.0 exceptiongroup 1.1.0 iniconfig 2.0.0 packaging 23.0 pip 22.0.4 pluggy 1.0.0 pytest 7.2.1 setuptools 58.1.0 tomli 2.0.1 Cersions of OS and pytest
- macOS 12.6.3
- python 3.10.4
- pytest 7.2.1