Python Testing with pytest

Writing Assertion Helper Functions

An assertion helper is a function that is used to wrap up a complicated assertion check. As an example, the Cards data class is set up such that two cards with different IDs will still report equality. If we wanted to have a stricter check, we could write a helper function called assert_identical like this:

ch2/test_helper.py

from cards import Card
import pytest


def assert_identical(c1: Card, c2: Card):
    __tracebackhide__ = True
    assert c1 == c2
    if c1.id != c2.id:
        pytest.fail(f"id's don't match. {c1.id} != {c2.id}")


def test_identical():
    c1 = Card("foo", id=123)
    c2 = Card("foo", id=123)
    assert_identical(c1, c2)


def test_identical_fail():
 c1 = Card( ...