Automate Test Logging in Python with a Simple Decorator

Why Automatic Logging Is Needed

When a test suite contains many test cases, each test often needs to log a start message, a success message, or a failure message, together with a timestamp, test name, and execution duration. Hard‑coding these log statements makes format changes cumbersome and mixes logging with test logic.

Core Idea: Wrap Test Functions with a Decorator

A Python decorator can inject logging before and after a test runs without modifying the test’s source code.

import functools
import logging
import time

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(levelname)s - %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S"
)

def log_test(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        logger = logging.getLogger(__name__)
        logger.info(f"▶ 开始执行测试: {func.__name__}")
        start_time = time.time()
        try:
            result = func(*args, **kwargs)
            elapsed = time.time() - start_time
            logger.info(f"✅ 测试通过: {func.__name__} | 耗时: {elapsed:.2f}s")
            return result
        except Exception as e:
            elapsed = time.time() - start_time
            logger.error(f"❌ 测试失败: {func.__name__} | 耗时: {elapsed:.2f}s | 错误: {e}")
            raise
    return wrapper

Usage Example

@log_test
def test_user_login_success():
    assert login("alice", "123456") is True

@log_test
def test_create_order():
    order_id = create_order(user_id=1001, items=["A", "B"])
    assert order_id > 0

@log_test
def test_api_timeout_should_fail():
    response = call_slow_api(timeout=1)
    assert response.status_code == 200  # expected to timeout

Sample Output

2026-01-24 21:40:01 - INFO - ▶ 开始执行测试: test_user_login_success
2026-01-24 21:40:01 - INFO - ✅ 测试通过: test_user_login_success | 耗时: 0.05s
2026-01-24 21:40:01 - INFO - ▶ 开始执行测试: test_create_order
2026-01-24 21:40:02 - INFO - ✅ 测试通过: test_create_order | 耗时: 0.82s
2026-01-24 21:40:02 - INFO - ▶ 开始执行测试: test_api_timeout_should_fail
2026-01-24 21:40:05 - ERROR - ❌ 测试失败: test_api_timeout_should_fail | 耗时: 3.01s | 错误: TimeoutError: API call timed out

Advanced Tips

Make the decorator configurable, e.g., @log_test(level="DEBUG"), to allow custom log levels or formats.

It works seamlessly with pytest; the decorator does not interfere with pytest’s assertion handling or reporting.

To write logs to a file, add filename="test.log" to logging.basicConfig.

Capture test arguments for richer context:

logger.info(f"▶ 执行测试: {func.__name__} (参数: {kwargs})")

.