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Testing & modern typing

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

5 matches

How to Flag Unexpected Diff Changes in Python

Compares two snapshot lists, detects unexpected differences, and returns a flag indicating whether the snapshot should be updated.

diffing snapshot-testing difflib

Python

import difflib

def snapshot_diff(before, after, intentional_changes=None):
    """Compare snapshots and flag only unexpected differences."""
    intentional_changes = intentional_changes or set()
    diff = list(difflib.unified_diff(before, after, lineterm=""))
    has_unexpected = False

    for line in diff:
      …

16 0 Open

Testing & modern typing medium

How to Mock a Factory Boy Model Instance in Python

Create a factory boy factory, then patch its Meta.model with a Mock to control instance behavior in tests.

factory-boy mocking unit-testing

Python

import factory
from dataclasses import dataclass
from unittest.mock import Mock, patch
import builtins


@dataclass
class User:
    name: str
    age: int


class UserFactory(factory.Factory):
    class Meta:
        model = User

    name = "Alice"
    age = 30


def get_user_name(user):
    return user.name


def ma…

15 0 Open

Testing & modern typing medium

How to Mock and Stub API Calls in Playwright E2E Tests with Python

This code demonstrates how to mock and stub API responses in Playwright end-to-end tests using Python's unittest.mock patch and Playwright's APIRequestContext.

playwright e2e-testing mocking

Python

import re
from unittest.mock import patch
from playwright.sync_api import sync_playwright

def verify_api_mock(page, mock_url, mock_response):
    with patch("playwright.sync_api.APIRequestContext.get") as mock_get:
        mock_get.return_value.json.return_value = mock_response
        mock_get.return_value.status_co…

13 0 Open

Testing & modern typing medium

How to Use Hypothesis Strategies for Lists of Text in Python

Generate random lists of non-empty strings with Hypothesis and verify that joining them with a comma-and-space separator meets expected length and containment invariants.

hypothesis property-based-testing strategies

Python

from hypothesis import given, strategies as st
from hypothesis import example


@given(st.lists(st.text(min_size=1, max_size=10), min_size=1, max_size=5))
def test_joined_string_length(items):
    """Each text is non-empty; a joined string should be at least as long
    as the number of items (separator adds character…

13 0 Open

Testing & modern typing medium

Use pytest fixture to mock a database connection in Python

This code shows how to use a pytest fixture and unittest.mock to replace a database connection with a Mock, enabling isolated tests without a real database.

pytest fixtures unittest.mock

Python

import pytest
import sqlite3
from unittest.mock import Mock

class Database:
    def __init__(self, connection):
        self.connection = connection

    def get_user(self, user_id):
        cursor = self.connection.cursor()
        cursor.execute("SELECT * FROM users WHERE id = ?", (user_id,))
        return cursor.…

19 0 Open

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