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Testing & modern typing

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

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How to Mock pathlib Path.read_text with mock_open in Python

Mock pathlib.Path.read_text using patch and mock_open to test file-reading code without touching the filesystem.

import pathlib
from unittest.mock import mock_open, patch

def read_config(filepath: pathlib.Path) -> str:
    """Read file content with pathlib."""
    return filepath.read_text()

if __name__ == "__main__":
    mock_data = "version: 1.0\nname: demo-app"
    
    with patch("pathlib.Path.open", mock_open(read_data=mo…

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Testing & modern typing easy

How to Use the pytest tmp_path Fixture for Temporary Directories

Use pytest's built-in tmp_path fixture to create a unique temporary directory per test for clean file I/O testing.

pytest tmp_path fixtures

Python

import pytest


def test_write_and_read_file(tmp_path):
    # tmp_path is a pytest fixture that provides a temporary directory
    # unique to each test invocation
    data_file = tmp_path / "data.txt"
    data_file.write_text("hello world")
    assert data_file.read_text() == "hello world"


def test_multiple_tmp_pat…

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Testing & modern typing easy

How to Write a Fast Smoke Test for a Critical Path in Python

A quick smoke test that validates the /health critical path executes fast enough, raising errors on wrong paths or slow responses.

smoke-test performance health-check

Python

import time

def smoke_test(path):
    if path != "/health":
        raise ValueError("Critical path expected /health")
    start = time.perf_counter()
    # Simulate the critical health check work
    time.sleep(0.01)
    elapsed = time.perf_counter() - start
    if elapsed > 0.05:
        raise RuntimeError("Health …

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