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Testing & modern typing

pytest basics, mocks, type hints, TypedDict, Protocol, and static-checking patterns.

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Testing & modern typing easy

How to mark known bugs with pytest xfail in Python

Use @pytest.mark.xfail to mark tests that are expected to fail due to known bugs, with optional strict mode to control pass/fail behavior.

pytest testing xfail
Python 
import pytest


def divide(a: int, b: int) -> float:
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero")
    return a / b


@pytest.mark.xfail(reason="Known bug: division returns int instead of float", strict=False)
def test_divide_integer_division():
    result = divide(10, 4)
    assert isinstanc…
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