Testing in Python

# test_calculator.py
import pytest
from calculator import add, divide

def test_add():
    assert add(2, 3) == 5
    assert add(-1, 1) == 0

def test_divide():
    assert divide(10, 2) == 5

def test_divide_by_zero():
    with pytest.raises(ZeroDivisionError):
        divide(10, 0)

import pytest

@pytest.fixture
def sample_user():
    return {"name": "Alice", "age": 30}

@pytest.fixture
def db_connection():
    conn = create_connection()
    yield conn  # Provide to test
    conn.close()  # Cleanup after test

def test_user_name(sample_user):
    assert sample_user["name"] == "Alice"

def test_database(db_connection):
    result = db_connection.query("SELECT 1")
    assert result is not None

from unittest.mock import Mock, patch, MagicMock

# Basic mock
mock = Mock()
mock.method.return_value = 42
assert mock.method() == 42

# Patch decorator
@patch('module.external_api')
def test_api_call(mock_api):
    mock_api.return_value = {"status": "ok"}
    result = call_api()
    assert result["status"] == "ok"
    mock_api.assert_called_once()

# Context manager
def test_file_read():
    with patch('builtins.open', mock_open(read_data='hello')):
        with open('test.txt') as f:
            assert f.read() == 'hello'

import pytest

@pytest.mark.parametrize("input,expected", [
    (2, 4),
    (3, 9),
    (4, 16),
    (-2, 4),
])
def test_square(input, expected):
    assert input ** 2 == expected

@pytest.mark.parametrize("a,b,expected", [
    (1, 2, 3),
    (0, 0, 0),
    (-1, 1, 0),
])
def test_add(a, b, expected):
    assert add(a, b) == expected

import pytest
import asyncio

@pytest.mark.asyncio
async def test_async_function():
    result = await async_operation()
    assert result == "expected"