如何在 try-except 语句中正确处理 pyodbc 错误

Question

我想知道我正在处理一个异常，该异常仅在数据库路径不正确时才引发，并且仅正确引发该错误反映在我的函数测试通过或失败中。目前，当任何错误包含在 else 子句中时，我的单元测试通过。

我怀疑我没有正确构造 try-except 语句以捕获正确的错误。对于pyodbc，我专门尝试捕获一个名为"pyodbc"的错误。错误"，但当前所有错误都会导致测试通过。

我希望测试失败，除非引发的错误是 except 子句中指定的错误。我不想有一个"包罗万象"的尝试。

def get_database():
    try:
        conn = pyodbc.connect(
            r'Driver={Microsoft Access Driver (*.mdb, *.accdb)};'
            r'DBQ=M:PathToDatabaseMy_Database.accdb;'
        )
        return conn
    except pyodbc.Error as err: # Only error I wanted passed for the test!
        raise err
@mock.patch('directory1.script1.pyodbc.connect')
def test_invalid_path_to_database(self, mock_conn):
    mock_conn.side_effect = pyodbc.Error
    # Passes no matter what exception is included in except clause!
    self.assertRaises(pyodbc.Error, get_database)  

Answer 1

这是一个工作示例，似乎可以捕获非pyodbc.Error错误。你能澄清你想做什么吗？

import pyodbc
import unittest
import mock
def get_database():
    try:
        conn = pyodbc.connect(
            r'Driver={Microsoft Access Driver (*.mdb, *.accdb)};'
            r'DBQ=M:PathToDatabaseMy_Database.accdb;'
        )
        return conn
    except pyodbc.Error as err: # Only error I wanted passed for the test!
        raise ValueError('Non pyodbc error')
class Test(unittest.TestCase):
    @mock.patch('pyodbc.connect')
    def test_invalid_path_to_database(self, mock_conn):
        mock_conn.side_effect = pyodbc.Error
        self.assertRaises(pyodbc.Error, get_database)
if __name__ == '__main__':
    unittest.main()

带输出

Traceback (most recent call last):
  File "/Users/henry/projects/stack/.venv/lib/python3.7/site-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
  File "example.py", line 21, in test_invalid_path_to_database
    self.assertRaises(pyodbc.Error, get_database)
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/unittest/case.py", line 743, in assertRaises
    return context.handle('assertRaises', args, kwargs)
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/unittest/case.py", line 178, in handle
    callable_obj(*args, **kwargs)
  File "example.py", line 13, in get_database
    raise ValueError('Non pyodbc error')
ValueError: Non pyodbc error
----------------------------------------------------------------------
Ran 1 test in 0.002s