项目初始化

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---
name: brand-voice
description: Build a source-derived writing style profile from real posts, essays, launch notes, docs, or site copy, then reuse that profile across content, outreach, and social workflows. Use when the user wants voice consistency without generic AI writing tropes.
metadata:
origin: ECC
---
# Brand Voice
Build a durable voice profile from real source material, then use that profile everywhere instead of re-deriving style from scratch or defaulting to generic AI copy.
## When to Activate
- the user wants content or outreach in a specific voice
- writing for X, LinkedIn, email, launch posts, threads, or product updates
- adapting a known author's tone across channels
- the existing content lane needs a reusable style system instead of one-off mimicry
## Source Priority
Use the strongest real source set available, in this order:
1. recent original X posts and threads
2. articles, essays, memos, launch notes, or newsletters
3. real outbound emails or DMs that worked
4. product docs, changelogs, README framing, and site copy
Do not use generic platform exemplars as source material.
## Collection Workflow
1. Gather 5 to 20 representative samples when available.
2. Prefer recent material over old material unless the user says the older writing is more canonical.
3. Separate "public launch voice" from "private working voice" if the source set clearly splits.
4. If live X access is available, use `x-api` to pull recent original posts before drafting.
5. If site copy matters, include the current ECC landing page and repo/plugin framing.
## What to Extract
- rhythm and sentence length
- compression vs explanation
- capitalization norms
- parenthetical use
- question frequency and purpose
- how sharply claims are made
- how often numbers, mechanisms, or receipts show up
- how transitions work
- what the author never does
## Output Contract
Produce a reusable `VOICE PROFILE` block that downstream skills can consume directly. Use the schema in [references/voice-profile-schema.md](references/voice-profile-schema.md).
Keep the profile structured and short enough to reuse in session context. The point is not literary criticism. The point is operational reuse.
## Affaan / ECC Defaults
If the user wants Affaan / ECC voice and live sources are thin, start here unless newer source material overrides it:
- direct, compressed, concrete
- specifics, mechanisms, receipts, and numbers beat adjectives
- parentheticals are for qualification, narrowing, or over-clarification
- capitalization is conventional unless there is a real reason to break it
- questions are rare and should not be used as bait
- tone can be sharp, blunt, skeptical, or dry
- transitions should feel earned, not smoothed over
## Hard Bans
Delete and rewrite any of these:
- fake curiosity hooks
- "not X, just Y"
- "no fluff"
- forced lowercase
- LinkedIn thought-leader cadence
- bait questions
- "Excited to share"
- generic founder-journey filler
- corny parentheticals
## Persistence Rules
- Reuse the latest confirmed `VOICE PROFILE` across related tasks in the same session.
- If the user asks for a durable artifact, save the profile in the requested workspace location or memory surface.
- Do not create repo-tracked files that store personal voice fingerprints unless the user explicitly asks for that.
## Downstream Use
Use this skill before or inside:
- `content-engine`
- `crosspost`
- `lead-intelligence`
- article or launch writing
- cold or warm outbound across X, LinkedIn, and email
If another skill already has a partial voice capture section, this skill is the canonical source of truth.

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# Voice Profile Schema
Use this exact structure when building a reusable voice profile:
```text
VOICE PROFILE
=============
Author:
Goal:
Confidence:
Source Set
- source 1
- source 2
- source 3
Rhythm
- short note on sentence length, pacing, and fragmentation
Compression
- how dense or explanatory the writing is
Capitalization
- conventional, mixed, or situational
Parentheticals
- how they are used and how they are not used
Question Use
- rare, frequent, rhetorical, direct, or mostly absent
Claim Style
- how claims are framed, supported, and sharpened
Preferred Moves
- concrete moves the author does use
Banned Moves
- specific patterns the author does not use
CTA Rules
- how, when, or whether to close with asks
Channel Notes
- X:
- LinkedIn:
- Email:
```
Guidelines:
- Keep the profile concrete and source-backed.
- Use short bullets, not essay paragraphs.
- Every banned move should be observable in the source set or explicitly requested by the user.
- If the source set conflicts, call out the split instead of averaging it into mush.

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---
name: python-patterns
description: Pythonic idioms, PEP 8 standards, type hints, and best practices for building robust, efficient, and maintainable Python applications.
metadata:
origin: ECC
---
# Python Development Patterns
Idiomatic Python patterns and best practices for building robust, efficient, and maintainable applications.
## When to Activate
- Writing new Python code
- Reviewing Python code
- Refactoring existing Python code
- Designing Python packages/modules
## Core Principles
### 1. Readability Counts
Python prioritizes readability. Code should be obvious and easy to understand.
```python
# Good: Clear and readable
def get_active_users(users: list[User]) -> list[User]:
"""Return only active users from the provided list."""
return [user for user in users if user.is_active]
# Bad: Clever but confusing
def get_active_users(u):
return [x for x in u if x.a]
```
### 2. Explicit is Better Than Implicit
Avoid magic; be clear about what your code does.
```python
# Good: Explicit configuration
import logging
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
# Bad: Hidden side effects
import some_module
some_module.setup() # What does this do?
```
### 3. EAFP - Easier to Ask Forgiveness Than Permission
Python prefers exception handling over checking conditions.
```python
# Good: EAFP style
def get_value(dictionary: dict, key: str, default_value: Any = None) -> Any:
try:
return dictionary[key]
except KeyError:
return default_value
# Bad: LBYL (Look Before You Leap) style
def get_value(dictionary: dict, key: str, default_value: Any = None) -> Any:
if key in dictionary:
return dictionary[key]
else:
return default_value
```
## Type Hints
### Basic Type Annotations
```python
from typing import Optional, List, Dict, Any
def process_user(
user_id: str,
data: Dict[str, Any],
active: bool = True
) -> Optional[User]:
"""Process a user and return the updated User or None."""
if not active:
return None
return User(user_id, data)
```
### Modern Type Hints (Python 3.9+)
```python
# Python 3.9+ - Use built-in types
def process_items(items: list[str]) -> dict[str, int]:
return {item: len(item) for item in items}
# Python 3.8 and earlier - Use typing module
from typing import List, Dict
def process_items(items: List[str]) -> Dict[str, int]:
return {item: len(item) for item in items}
```
### Type Aliases and TypeVar
```python
from typing import TypeVar, Union
# Type alias for complex types
JSON = Union[dict[str, Any], list[Any], str, int, float, bool, None]
def parse_json(data: str) -> JSON:
return json.loads(data)
# Generic types
T = TypeVar('T')
def first(items: list[T]) -> T | None:
"""Return the first item or None if list is empty."""
return items[0] if items else None
```
### Protocol-Based Duck Typing
```python
from typing import Protocol
class Renderable(Protocol):
def render(self) -> str:
"""Render the object to a string."""
def render_all(items: list[Renderable]) -> str:
"""Render all items that implement the Renderable protocol."""
return "\n".join(item.render() for item in items)
```
## Error Handling Patterns
### Specific Exception Handling
```python
# Good: Catch specific exceptions
def load_config(path: str) -> Config:
try:
with open(path) as f:
return Config.from_json(f.read())
except FileNotFoundError as e:
raise ConfigError(f"Config file not found: {path}") from e
except json.JSONDecodeError as e:
raise ConfigError(f"Invalid JSON in config: {path}") from e
# Bad: Bare except
def load_config(path: str) -> Config:
try:
with open(path) as f:
return Config.from_json(f.read())
except:
return None # Silent failure!
```
### Exception Chaining
```python
def process_data(data: str) -> Result:
try:
parsed = json.loads(data)
except json.JSONDecodeError as e:
# Chain exceptions to preserve the traceback
raise ValueError(f"Failed to parse data: {data}") from e
```
### Custom Exception Hierarchy
```python
class AppError(Exception):
"""Base exception for all application errors."""
pass
class ValidationError(AppError):
"""Raised when input validation fails."""
pass
class NotFoundError(AppError):
"""Raised when a requested resource is not found."""
pass
# Usage
def get_user(user_id: str) -> User:
user = db.find_user(user_id)
if not user:
raise NotFoundError(f"User not found: {user_id}")
return user
```
## Context Managers
### Resource Management
```python
# Good: Using context managers
def process_file(path: str) -> str:
with open(path, 'r') as f:
return f.read()
# Bad: Manual resource management
def process_file(path: str) -> str:
f = open(path, 'r')
try:
return f.read()
finally:
f.close()
```
### Custom Context Managers
```python
from contextlib import contextmanager
@contextmanager
def timer(name: str):
"""Context manager to time a block of code."""
start = time.perf_counter()
yield
elapsed = time.perf_counter() - start
print(f"{name} took {elapsed:.4f} seconds")
# Usage
with timer("data processing"):
process_large_dataset()
```
### Context Manager Classes
```python
class DatabaseTransaction:
def __init__(self, connection):
self.connection = connection
def __enter__(self):
self.connection.begin_transaction()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
if exc_type is None:
self.connection.commit()
else:
self.connection.rollback()
return False # Don't suppress exceptions
# Usage
with DatabaseTransaction(conn):
user = conn.create_user(user_data)
conn.create_profile(user.id, profile_data)
```
## Comprehensions and Generators
### List Comprehensions
```python
# Good: List comprehension for simple transformations
names = [user.name for user in users if user.is_active]
# Bad: Manual loop
names = []
for user in users:
if user.is_active:
names.append(user.name)
# Complex comprehensions should be expanded
# Bad: Too complex
result = [x * 2 for x in items if x > 0 if x % 2 == 0]
# Good: Use a generator function
def filter_and_transform(items: Iterable[int]) -> list[int]:
result = []
for x in items:
if x > 0 and x % 2 == 0:
result.append(x * 2)
return result
```
### Generator Expressions
```python
# Good: Generator for lazy evaluation
total = sum(x * x for x in range(1_000_000))
# Bad: Creates large intermediate list
total = sum([x * x for x in range(1_000_000)])
```
### Generator Functions
```python
def read_large_file(path: str) -> Iterator[str]:
"""Read a large file line by line."""
with open(path) as f:
for line in f:
yield line.strip()
# Usage
for line in read_large_file("huge.txt"):
process(line)
```
## Data Classes and Named Tuples
### Data Classes
```python
from dataclasses import dataclass, field
from datetime import datetime
@dataclass
class User:
"""User entity with automatic __init__, __repr__, and __eq__."""
id: str
name: str
email: str
created_at: datetime = field(default_factory=datetime.now)
is_active: bool = True
# Usage
user = User(
id="123",
name="Alice",
email="alice@example.com"
)
```
### Data Classes with Validation
```python
@dataclass
class User:
email: str
age: int
def __post_init__(self):
# Validate email format
if "@" not in self.email:
raise ValueError(f"Invalid email: {self.email}")
# Validate age range
if self.age < 0 or self.age > 150:
raise ValueError(f"Invalid age: {self.age}")
```
### Named Tuples
```python
from typing import NamedTuple
class Point(NamedTuple):
"""Immutable 2D point."""
x: float
y: float
def distance(self, other: 'Point') -> float:
return ((self.x - other.x) ** 2 + (self.y - other.y) ** 2) ** 0.5
# Usage
p1 = Point(0, 0)
p2 = Point(3, 4)
print(p1.distance(p2)) # 5.0
```
## Decorators
### Function Decorators
```python
import functools
import time
def timer(func: Callable) -> Callable:
"""Decorator to time function execution."""
@functools.wraps(func)
def wrapper(*args, **kwargs):
start = time.perf_counter()
result = func(*args, **kwargs)
elapsed = time.perf_counter() - start
print(f"{func.__name__} took {elapsed:.4f}s")
return result
return wrapper
@timer
def slow_function():
time.sleep(1)
# slow_function() prints: slow_function took 1.0012s
```
### Parameterized Decorators
```python
def repeat(times: int):
"""Decorator to repeat a function multiple times."""
def decorator(func: Callable) -> Callable:
@functools.wraps(func)
def wrapper(*args, **kwargs):
results = []
for _ in range(times):
results.append(func(*args, **kwargs))
return results
return wrapper
return decorator
@repeat(times=3)
def greet(name: str) -> str:
return f"Hello, {name}!"
# greet("Alice") returns ["Hello, Alice!", "Hello, Alice!", "Hello, Alice!"]
```
### Class-Based Decorators
```python
class CountCalls:
"""Decorator that counts how many times a function is called."""
def __init__(self, func: Callable):
functools.update_wrapper(self, func)
self.func = func
self.count = 0
def __call__(self, *args, **kwargs):
self.count += 1
print(f"{self.func.__name__} has been called {self.count} times")
return self.func(*args, **kwargs)
@CountCalls
def process():
pass
# Each call to process() prints the call count
```
## Concurrency Patterns
### Threading for I/O-Bound Tasks
```python
import concurrent.futures
import threading
def fetch_url(url: str) -> str:
"""Fetch a URL (I/O-bound operation)."""
import urllib.request
with urllib.request.urlopen(url) as response:
return response.read().decode()
def fetch_all_urls(urls: list[str]) -> dict[str, str]:
"""Fetch multiple URLs concurrently using threads."""
with concurrent.futures.ThreadPoolExecutor(max_workers=10) as executor:
future_to_url = {executor.submit(fetch_url, url): url for url in urls}
results = {}
for future in concurrent.futures.as_completed(future_to_url):
url = future_to_url[future]
try:
results[url] = future.result()
except Exception as e:
results[url] = f"Error: {e}"
return results
```
### Multiprocessing for CPU-Bound Tasks
```python
def process_data(data: list[int]) -> int:
"""CPU-intensive computation."""
return sum(x ** 2 for x in data)
def process_all(datasets: list[list[int]]) -> list[int]:
"""Process multiple datasets using multiple processes."""
with concurrent.futures.ProcessPoolExecutor() as executor:
results = list(executor.map(process_data, datasets))
return results
```
### Async/Await for Concurrent I/O
```python
import asyncio
async def fetch_async(url: str) -> str:
"""Fetch a URL asynchronously."""
import aiohttp
async with aiohttp.ClientSession() as session:
async with session.get(url) as response:
return await response.text()
async def fetch_all(urls: list[str]) -> dict[str, str]:
"""Fetch multiple URLs concurrently."""
tasks = [fetch_async(url) for url in urls]
results = await asyncio.gather(*tasks, return_exceptions=True)
return dict(zip(urls, results))
```
## Package Organization
### Standard Project Layout
```
myproject/
├── src/
│ └── mypackage/
│ ├── __init__.py
│ ├── main.py
│ ├── api/
│ │ ├── __init__.py
│ │ └── routes.py
│ ├── models/
│ │ ├── __init__.py
│ │ └── user.py
│ └── utils/
│ ├── __init__.py
│ └── helpers.py
├── tests/
│ ├── __init__.py
│ ├── conftest.py
│ ├── test_api.py
│ └── test_models.py
├── pyproject.toml
├── README.md
└── .gitignore
```
### Import Conventions
```python
# Good: Import order - stdlib, third-party, local
import os
import sys
from pathlib import Path
import requests
from fastapi import FastAPI
from mypackage.models import User
from mypackage.utils import format_name
# Good: Use isort for automatic import sorting
# pip install isort
```
### __init__.py for Package Exports
```python
# mypackage/__init__.py
"""mypackage - A sample Python package."""
__version__ = "1.0.0"
# Export main classes/functions at package level
from mypackage.models import User, Post
from mypackage.utils import format_name
__all__ = ["User", "Post", "format_name"]
```
## Memory and Performance
### Using __slots__ for Memory Efficiency
```python
# Bad: Regular class uses __dict__ (more memory)
class Point:
def __init__(self, x: float, y: float):
self.x = x
self.y = y
# Good: __slots__ reduces memory usage
class Point:
__slots__ = ['x', 'y']
def __init__(self, x: float, y: float):
self.x = x
self.y = y
```
### Generator for Large Data
```python
# Bad: Returns full list in memory
def read_lines(path: str) -> list[str]:
with open(path) as f:
return [line.strip() for line in f]
# Good: Yields lines one at a time
def read_lines(path: str) -> Iterator[str]:
with open(path) as f:
for line in f:
yield line.strip()
```
### Avoid String Concatenation in Loops
```python
# Bad: O(n²) due to string immutability
result = ""
for item in items:
result += str(item)
# Good: O(n) using join
result = "".join(str(item) for item in items)
# Good: Using StringIO for building
from io import StringIO
buffer = StringIO()
for item in items:
buffer.write(str(item))
result = buffer.getvalue()
```
## Python Tooling Integration
### Essential Commands
```bash
# Code formatting
black .
isort .
# Linting
ruff check .
pylint mypackage/
# Type checking
mypy .
# Testing
pytest --cov=mypackage --cov-report=html
# Security scanning
bandit -r .
# Dependency management
pip-audit
safety check
```
### pyproject.toml Configuration
```toml
[project]
name = "mypackage"
version = "1.0.0"
requires-python = ">=3.9"
dependencies = [
"requests>=2.31.0",
"pydantic>=2.0.0",
]
[project.optional-dependencies]
dev = [
"pytest>=7.4.0",
"pytest-cov>=4.1.0",
"black>=23.0.0",
"ruff>=0.1.0",
"mypy>=1.5.0",
]
[tool.black]
line-length = 88
target-version = ['py39']
[tool.ruff]
line-length = 88
select = ["E", "F", "I", "N", "W"]
[tool.mypy]
python_version = "3.9"
warn_return_any = true
warn_unused_configs = true
disallow_untyped_defs = true
[tool.pytest.ini_options]
testpaths = ["tests"]
addopts = "--cov=mypackage --cov-report=term-missing"
```
## Quick Reference: Python Idioms
| Idiom | Description |
|-------|-------------|
| EAFP | Easier to Ask Forgiveness than Permission |
| Context managers | Use `with` for resource management |
| List comprehensions | For simple transformations |
| Generators | For lazy evaluation and large datasets |
| Type hints | Annotate function signatures |
| Dataclasses | For data containers with auto-generated methods |
| `__slots__` | For memory optimization |
| f-strings | For string formatting (Python 3.6+) |
| `pathlib.Path` | For path operations (Python 3.4+) |
| `enumerate` | For index-element pairs in loops |
## Anti-Patterns to Avoid
```python
# Bad: Mutable default arguments
def append_to(item, items=[]):
items.append(item)
return items
# Good: Use None and create new list
def append_to(item, items=None):
if items is None:
items = []
items.append(item)
return items
# Bad: Checking type with type()
if type(obj) == list:
process(obj)
# Good: Use isinstance
if isinstance(obj, list):
process(obj)
# Bad: Comparing to None with ==
if value == None:
process()
# Good: Use is
if value is None:
process()
# Bad: from module import *
from os.path import *
# Good: Explicit imports
from os.path import join, exists
# Bad: Bare except
try:
risky_operation()
except:
pass
# Good: Specific exception
try:
risky_operation()
except SpecificError as e:
logger.error(f"Operation failed: {e}")
```
__Remember__: Python code should be readable, explicit, and follow the principle of least surprise. When in doubt, prioritize clarity over cleverness.

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---
name: python-testing
description: Python testing strategies using pytest, TDD methodology, fixtures, mocking, parametrization, and coverage requirements.
metadata:
origin: ECC
---
# Python Testing Patterns
Comprehensive testing strategies for Python applications using pytest, TDD methodology, and best practices.
## When to Activate
- Writing new Python code (follow TDD: red, green, refactor)
- Designing test suites for Python projects
- Reviewing Python test coverage
- Setting up testing infrastructure
## Core Testing Philosophy
### Test-Driven Development (TDD)
Always follow the TDD cycle:
1. **RED**: Write a failing test for the desired behavior
2. **GREEN**: Write minimal code to make the test pass
3. **REFACTOR**: Improve code while keeping tests green
```python
# Step 1: Write failing test (RED)
def test_add_numbers():
result = add(2, 3)
assert result == 5
# Step 2: Write minimal implementation (GREEN)
def add(a, b):
return a + b
# Step 3: Refactor if needed (REFACTOR)
```
### Coverage Requirements
- **Target**: 80%+ code coverage
- **Critical paths**: 100% coverage required
- Use `pytest --cov` to measure coverage
```bash
pytest --cov=mypackage --cov-report=term-missing --cov-report=html
```
## pytest Fundamentals
### Basic Test Structure
```python
import pytest
def test_addition():
"""Test basic addition."""
assert 2 + 2 == 4
def test_string_uppercase():
"""Test string uppercasing."""
text = "hello"
assert text.upper() == "HELLO"
def test_list_append():
"""Test list append."""
items = [1, 2, 3]
items.append(4)
assert 4 in items
assert len(items) == 4
```
### Assertions
```python
# Equality
assert result == expected
# Inequality
assert result != unexpected
# Truthiness
assert result # Truthy
assert not result # Falsy
assert result is True # Exactly True
assert result is False # Exactly False
assert result is None # Exactly None
# Membership
assert item in collection
assert item not in collection
# Comparisons
assert result > 0
assert 0 <= result <= 100
# Type checking
assert isinstance(result, str)
# Exception testing (preferred approach)
with pytest.raises(ValueError):
raise ValueError("error message")
# Check exception message
with pytest.raises(ValueError, match="invalid input"):
raise ValueError("invalid input provided")
# Check exception attributes
with pytest.raises(ValueError) as exc_info:
raise ValueError("error message")
assert str(exc_info.value) == "error message"
```
## Fixtures
### Basic Fixture Usage
```python
import pytest
@pytest.fixture
def sample_data():
"""Fixture providing sample data."""
return {"name": "Alice", "age": 30}
def test_sample_data(sample_data):
"""Test using the fixture."""
assert sample_data["name"] == "Alice"
assert sample_data["age"] == 30
```
### Fixture with Setup/Teardown
```python
@pytest.fixture
def database():
"""Fixture with setup and teardown."""
# Setup
db = Database(":memory:")
db.create_tables()
db.insert_test_data()
yield db # Provide to test
# Teardown
db.close()
def test_database_query(database):
"""Test database operations."""
result = database.query("SELECT * FROM users")
assert len(result) > 0
```
### Fixture Scopes
```python
# Function scope (default) - runs for each test
@pytest.fixture
def temp_file():
with open("temp.txt", "w") as f:
yield f
os.remove("temp.txt")
# Module scope - runs once per module
@pytest.fixture(scope="module")
def module_db():
db = Database(":memory:")
db.create_tables()
yield db
db.close()
# Session scope - runs once per test session
@pytest.fixture(scope="session")
def shared_resource():
resource = ExpensiveResource()
yield resource
resource.cleanup()
```
### Fixture with Parameters
```python
@pytest.fixture(params=[1, 2, 3])
def number(request):
"""Parameterized fixture."""
return request.param
def test_numbers(number):
"""Test runs 3 times, once for each parameter."""
assert number > 0
```
### Using Multiple Fixtures
```python
@pytest.fixture
def user():
return User(id=1, name="Alice")
@pytest.fixture
def admin():
return User(id=2, name="Admin", role="admin")
def test_user_admin_interaction(user, admin):
"""Test using multiple fixtures."""
assert admin.can_manage(user)
```
### Autouse Fixtures
```python
@pytest.fixture(autouse=True)
def reset_config():
"""Automatically runs before every test."""
Config.reset()
yield
Config.cleanup()
def test_without_fixture_call():
# reset_config runs automatically
assert Config.get_setting("debug") is False
```
### Conftest.py for Shared Fixtures
```python
# tests/conftest.py
import pytest
@pytest.fixture
def client():
"""Shared fixture for all tests."""
app = create_app(testing=True)
with app.test_client() as client:
yield client
@pytest.fixture
def auth_headers(client):
"""Generate auth headers for API testing."""
response = client.post("/api/login", json={
"username": "test",
"password": "test"
})
token = response.json["token"]
return {"Authorization": f"Bearer {token}"}
```
## Parametrization
### Basic Parametrization
```python
@pytest.mark.parametrize("input,expected", [
("hello", "HELLO"),
("world", "WORLD"),
("PyThOn", "PYTHON"),
])
def test_uppercase(input, expected):
"""Test runs 3 times with different inputs."""
assert input.upper() == expected
```
### Multiple Parameters
```python
@pytest.mark.parametrize("a,b,expected", [
(2, 3, 5),
(0, 0, 0),
(-1, 1, 0),
(100, 200, 300),
])
def test_add(a, b, expected):
"""Test addition with multiple inputs."""
assert add(a, b) == expected
```
### Parametrize with IDs
```python
@pytest.mark.parametrize("input,expected", [
("valid@email.com", True),
("invalid", False),
("@no-domain.com", False),
], ids=["valid-email", "missing-at", "missing-domain"])
def test_email_validation(input, expected):
"""Test email validation with readable test IDs."""
assert is_valid_email(input) is expected
```
### Parametrized Fixtures
```python
@pytest.fixture(params=["sqlite", "postgresql", "mysql"])
def db(request):
"""Test against multiple database backends."""
if request.param == "sqlite":
return Database(":memory:")
elif request.param == "postgresql":
return Database("postgresql://localhost/test")
elif request.param == "mysql":
return Database("mysql://localhost/test")
def test_database_operations(db):
"""Test runs 3 times, once for each database."""
result = db.query("SELECT 1")
assert result is not None
```
## Markers and Test Selection
### Custom Markers
```python
# Mark slow tests
@pytest.mark.slow
def test_slow_operation():
time.sleep(5)
# Mark integration tests
@pytest.mark.integration
def test_api_integration():
response = requests.get("https://api.example.com")
assert response.status_code == 200
# Mark unit tests
@pytest.mark.unit
def test_unit_logic():
assert calculate(2, 3) == 5
```
### Run Specific Tests
```bash
# Run only fast tests
pytest -m "not slow"
# Run only integration tests
pytest -m integration
# Run integration or slow tests
pytest -m "integration or slow"
# Run tests marked as unit but not slow
pytest -m "unit and not slow"
```
### Configure Markers in pytest.ini
```ini
[pytest]
markers =
slow: marks tests as slow
integration: marks tests as integration tests
unit: marks tests as unit tests
django: marks tests as requiring Django
```
## Mocking and Patching
### Mocking Functions
```python
from unittest.mock import patch, Mock
@patch("mypackage.external_api_call")
def test_with_mock(api_call_mock):
"""Test with mocked external API."""
api_call_mock.return_value = {"status": "success"}
result = my_function()
api_call_mock.assert_called_once()
assert result["status"] == "success"
```
### Mocking Return Values
```python
@patch("mypackage.Database.connect")
def test_database_connection(connect_mock):
"""Test with mocked database connection."""
connect_mock.return_value = MockConnection()
db = Database()
db.connect()
connect_mock.assert_called_once_with("localhost")
```
### Mocking Exceptions
```python
@patch("mypackage.api_call")
def test_api_error_handling(api_call_mock):
"""Test error handling with mocked exception."""
api_call_mock.side_effect = ConnectionError("Network error")
with pytest.raises(ConnectionError):
api_call()
api_call_mock.assert_called_once()
```
### Mocking Context Managers
```python
@patch("builtins.open", new_callable=mock_open)
def test_file_reading(mock_file):
"""Test file reading with mocked open."""
mock_file.return_value.read.return_value = "file content"
result = read_file("test.txt")
mock_file.assert_called_once_with("test.txt", "r")
assert result == "file content"
```
### Using Autospec
```python
@patch("mypackage.DBConnection", autospec=True)
def test_autospec(db_mock):
"""Test with autospec to catch API misuse."""
db = db_mock.return_value
db.query("SELECT * FROM users")
# This would fail if DBConnection doesn't have query method
db_mock.assert_called_once()
```
### Mock Class Instances
```python
class TestUserService:
@patch("mypackage.UserRepository")
def test_create_user(self, repo_mock):
"""Test user creation with mocked repository."""
repo_mock.return_value.save.return_value = User(id=1, name="Alice")
service = UserService(repo_mock.return_value)
user = service.create_user(name="Alice")
assert user.name == "Alice"
repo_mock.return_value.save.assert_called_once()
```
### Mock Property
```python
@pytest.fixture
def mock_config():
"""Create a mock with a property."""
config = Mock()
type(config).debug = PropertyMock(return_value=True)
type(config).api_key = PropertyMock(return_value="test-key")
return config
def test_with_mock_config(mock_config):
"""Test with mocked config properties."""
assert mock_config.debug is True
assert mock_config.api_key == "test-key"
```
## Testing Async Code
### Async Tests with pytest-asyncio
```python
import pytest
@pytest.mark.asyncio
async def test_async_function():
"""Test async function."""
result = await async_add(2, 3)
assert result == 5
@pytest.mark.asyncio
async def test_async_with_fixture(async_client):
"""Test async with async fixture."""
response = await async_client.get("/api/users")
assert response.status_code == 200
```
### Async Fixture
```python
@pytest.fixture
async def async_client():
"""Async fixture providing async test client."""
app = create_app()
async with app.test_client() as client:
yield client
@pytest.mark.asyncio
async def test_api_endpoint(async_client):
"""Test using async fixture."""
response = await async_client.get("/api/data")
assert response.status_code == 200
```
### Mocking Async Functions
```python
@pytest.mark.asyncio
@patch("mypackage.async_api_call")
async def test_async_mock(api_call_mock):
"""Test async function with mock."""
api_call_mock.return_value = {"status": "ok"}
result = await my_async_function()
api_call_mock.assert_awaited_once()
assert result["status"] == "ok"
```
## Testing Exceptions
### Testing Expected Exceptions
```python
def test_divide_by_zero():
"""Test that dividing by zero raises ZeroDivisionError."""
with pytest.raises(ZeroDivisionError):
divide(10, 0)
def test_custom_exception():
"""Test custom exception with message."""
with pytest.raises(ValueError, match="invalid input"):
validate_input("invalid")
```
### Testing Exception Attributes
```python
def test_exception_with_details():
"""Test exception with custom attributes."""
with pytest.raises(CustomError) as exc_info:
raise CustomError("error", code=400)
assert exc_info.value.code == 400
assert "error" in str(exc_info.value)
```
## Testing Side Effects
### Testing File Operations
```python
import tempfile
import os
def test_file_processing():
"""Test file processing with temp file."""
with tempfile.NamedTemporaryFile(mode='w', delete=False, suffix='.txt') as f:
f.write("test content")
temp_path = f.name
try:
result = process_file(temp_path)
assert result == "processed: test content"
finally:
os.unlink(temp_path)
```
### Testing with pytest's tmp_path Fixture
```python
def test_with_tmp_path(tmp_path):
"""Test using pytest's built-in temp path fixture."""
test_file = tmp_path / "test.txt"
test_file.write_text("hello world")
result = process_file(str(test_file))
assert result == "hello world"
# tmp_path automatically cleaned up
```
### Testing with tmpdir Fixture
```python
def test_with_tmpdir(tmpdir):
"""Test using pytest's tmpdir fixture."""
test_file = tmpdir.join("test.txt")
test_file.write("data")
result = process_file(str(test_file))
assert result == "data"
```
## Test Organization
### Directory Structure
```
tests/
├── conftest.py # Shared fixtures
├── __init__.py
├── unit/ # Unit tests
│ ├── __init__.py
│ ├── test_models.py
│ ├── test_utils.py
│ └── test_services.py
├── integration/ # Integration tests
│ ├── __init__.py
│ ├── test_api.py
│ └── test_database.py
└── e2e/ # End-to-end tests
├── __init__.py
└── test_user_flow.py
```
### Test Classes
```python
class TestUserService:
"""Group related tests in a class."""
@pytest.fixture(autouse=True)
def setup(self):
"""Setup runs before each test in this class."""
self.service = UserService()
def test_create_user(self):
"""Test user creation."""
user = self.service.create_user("Alice")
assert user.name == "Alice"
def test_delete_user(self):
"""Test user deletion."""
user = User(id=1, name="Bob")
self.service.delete_user(user)
assert not self.service.user_exists(1)
```
## Best Practices
### DO
- **Follow TDD**: Write tests before code (red-green-refactor)
- **Test one thing**: Each test should verify a single behavior
- **Use descriptive names**: `test_user_login_with_invalid_credentials_fails`
- **Use fixtures**: Eliminate duplication with fixtures
- **Mock external dependencies**: Don't depend on external services
- **Test edge cases**: Empty inputs, None values, boundary conditions
- **Aim for 80%+ coverage**: Focus on critical paths
- **Keep tests fast**: Use marks to separate slow tests
### DON'T
- **Don't test implementation**: Test behavior, not internals
- **Don't use complex conditionals in tests**: Keep tests simple
- **Don't ignore test failures**: All tests must pass
- **Don't test third-party code**: Trust libraries to work
- **Don't share state between tests**: Tests should be independent
- **Don't catch exceptions in tests**: Use `pytest.raises`
- **Don't use print statements**: Use assertions and pytest output
- **Don't write tests that are too brittle**: Avoid over-specific mocks
## Common Patterns
### Testing API Endpoints (FastAPI/Flask)
```python
@pytest.fixture
def client():
app = create_app(testing=True)
return app.test_client()
def test_get_user(client):
response = client.get("/api/users/1")
assert response.status_code == 200
assert response.json["id"] == 1
def test_create_user(client):
response = client.post("/api/users", json={
"name": "Alice",
"email": "alice@example.com"
})
assert response.status_code == 201
assert response.json["name"] == "Alice"
```
### Testing Database Operations
```python
@pytest.fixture
def db_session():
"""Create a test database session."""
session = Session(bind=engine)
session.begin_nested()
yield session
session.rollback()
session.close()
def test_create_user(db_session):
user = User(name="Alice", email="alice@example.com")
db_session.add(user)
db_session.commit()
retrieved = db_session.query(User).filter_by(name="Alice").first()
assert retrieved.email == "alice@example.com"
```
### Testing Class Methods
```python
class TestCalculator:
@pytest.fixture
def calculator(self):
return Calculator()
def test_add(self, calculator):
assert calculator.add(2, 3) == 5
def test_divide_by_zero(self, calculator):
with pytest.raises(ZeroDivisionError):
calculator.divide(10, 0)
```
## pytest Configuration
### pytest.ini
```ini
[pytest]
testpaths = tests
python_files = test_*.py
python_classes = Test*
python_functions = test_*
addopts =
--strict-markers
--disable-warnings
--cov=mypackage
--cov-report=term-missing
--cov-report=html
markers =
slow: marks tests as slow
integration: marks tests as integration tests
unit: marks tests as unit tests
```
### pyproject.toml
```toml
[tool.pytest.ini_options]
testpaths = ["tests"]
python_files = ["test_*.py"]
python_classes = ["Test*"]
python_functions = ["test_*"]
addopts = [
"--strict-markers",
"--cov=mypackage",
"--cov-report=term-missing",
"--cov-report=html",
]
markers = [
"slow: marks tests as slow",
"integration: marks tests as integration tests",
"unit: marks tests as unit tests",
]
```
## Running Tests
```bash
# Run all tests
pytest
# Run specific file
pytest tests/test_utils.py
# Run specific test
pytest tests/test_utils.py::test_function
# Run with verbose output
pytest -v
# Run with coverage
pytest --cov=mypackage --cov-report=html
# Run only fast tests
pytest -m "not slow"
# Run until first failure
pytest -x
# Run and stop on N failures
pytest --maxfail=3
# Run last failed tests
pytest --lf
# Run tests with pattern
pytest -k "test_user"
# Run with debugger on failure
pytest --pdb
```
## Quick Reference
| Pattern | Usage |
|---------|-------|
| `pytest.raises()` | Test expected exceptions |
| `@pytest.fixture()` | Create reusable test fixtures |
| `@pytest.mark.parametrize()` | Run tests with multiple inputs |
| `@pytest.mark.slow` | Mark slow tests |
| `pytest -m "not slow"` | Skip slow tests |
| `@patch()` | Mock functions and classes |
| `tmp_path` fixture | Automatic temp directory |
| `pytest --cov` | Generate coverage report |
| `assert` | Simple and readable assertions |
**Remember**: Tests are code too. Keep them clean, readable, and maintainable. Good tests catch bugs; great tests prevent them.