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Testing & modern typing

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

3 matches

How to Assert Exceptions in Python with pytest.raises

Use pytest.raises as a context manager to assert that a function raises an expected exception and inspect its message in pytest tests.

pytest testing exceptions

Python

import pytest

def divide(a, b):
    if b == 0:
        raise ValueError("Cannot divide by zero")
    return a / b

def test_divide_by_zero():
    with pytest.raises(ValueError) as exc_info:
        divide(10, 0)
    assert str(exc_info.value) == "Cannot divide by zero"
    assert "zero" in str(exc_info.value)

def te…

14 0 Open

Testing & modern typing easy

How to Compare Floats in pytest with approx

Uses pytest.approx to compare floating-point numbers with tolerance, avoiding precision issues.

pytest floating-point testing

Python

import pytest

def test_float_addition():
    result = 0.1 + 0.2
    expected = 0.3
    assert result == pytest.approx(expected)

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Testing & modern typing easy

How to Use mock.assert_called_with in Python

Verify that a MagicMock received a call with specific positional and keyword arguments using assert_called_with in unittest.

unittest mock testing

Python

import unittest
from unittest.mock import MagicMock

class TestMockAssertions(unittest.TestCase):
    def test_assert_called_with(self):
        # Create a mock object
        mock = MagicMock()

        # Call the mock with specific arguments
        mock.send_email("alice@example.com", subject="Greetings", body="Hel…

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