Pytest测试发现触发sqlite3.OperationalError：无法打开数据库文件

Question

我有以下代码：

# config.py

from yaml import load, SafeLoader
from loguru import logger

""" Populate custom configuration for the
    SERVICE
    component
"""

APPNAME="acceloop-search-engine"

@logger.catch
def _get_field(config, fieldname):
  """Get specified field from yaml config file

  Args:
      config (dict): dictionary containing the parsed config yaml
      fieldname (str): the name of the field to be searched

  Returns:
      str: the value corresponding to the given field name
  """
  if fieldname not in config:
    raise SystemExit(f"No field named {fieldname} is present in yaml configuration file, please add it.")
  
  if not config[fieldname]:
    raise SystemExit(f"Field {fieldname} is present in yaml configuration file, but must not be empty string, null or None. Please correctly evaluate it.")

  return config[fieldname]

@logger.catch
def _get_loader():
  """Get customizable yaml loader

  Returns:
      loader: customized yaml loader
  """
  loader = SafeLoader
  return loader

@logger.catch
def _get_config(config_filename):
  """Get dictionary containing the parsed yaml config file

  Returns:
      dict: dictionary containing the parsed config yaml
  """
  return load(open(config_filename, "rb"), Loader=_get_loader())


class Config(object):

  def __new__(cls):
    if not hasattr(cls, "instance"):
      cls.instance = super(Config, cls).__new__(cls)
      cls.instance._init_singleton()
    return cls.instance
  
  @logger.catch
  def _init_singleton(self):
    try:
      __config = _get_config("config.yml")
    except Exception as error:
      raise SystemExit(f"Error while loading yaml config file: {error}")

    __app_config = _get_field(__config, "app")
    
    self.__table_db_path = _get_field(__app_config, "table-db-path")

  @property
  def table_db_path(self):
    return self.__table_db_path

此文件声明一个单例配置对象，该对象读取各种字段（为了简洁起见，此处已删除），包括 table-db-path。

# database.py

import sqlite3
from urllib.request import pathname2url
from .config import Config

try:
    dburi = "file:{}?mode=r".format(pathname2url(Config().table_db_path))
    LOCAL_SESSION = sqlite3.connect(dburi, uri=True)
except sqlite3.OperationalError:
    raise SystemExit(f"No db {Config().table_db_path} found. Please create it using the correct service.")

创建与 sqlite3 数据库的连接的简单类。

# test_database.py

from src.database import LOCAL_SESSION

def test_should_return_true_when_read_from_db_is_given():
    with LOCAL_SESSION.cursor() as cursor:
        cursor.execute("""
                        SELECT count(*) AS tot
                        FROM table
                        """)
        assert cursor.fetchone()[0] == 1

简单的测试文件，应检查表中是否只有一条记录。

# conftest.py

import pytest
from unittest.mock import patch
from src.config import Config

@pytest.fixture(scope="session", autouse=True)
def mock_config_table_db_path():
    with patch.object(Config, "table_db_path", "./tests/resources/ase_service.db"):
        yield

print("CONFTEST Loaded")

最后，我尝试修补conftest.py中的Config().table_db_path类属性。

Conftest 已正确加载其他参数，但此参数奇怪地触发

sqlite3.OperationalError：无法打开数据库文件

当 pytest 尝试发现测试时出错，导致该测试无法运行。奇怪的是，如果我检查 Config().table_db_path 的值，它是未修补的值，而不是修补的值。 有谁知道为什么会发生这种情况？

Answer 1

经过一番挖掘并访问 pytest github后，问题出在database.py文件上。当数据库文件导入到 test_database.py 中时，代码会自动执行，从而逃避猴子修补。我解决了创建提供准备连接的上下文管理器类的问题。