如何在try-except語句中正確處理Pyodbc錯誤

Question

我想知道，我正在處理一個僅在數據庫路徑不正確時引發的異常，而正確引發該異常僅反映在對函數的測試通過或未通過中。 當前，當任何錯誤包含在err子句之外時，我的單元測試就會通過。

我懷疑我沒有正確構造try-except語句來捕獲正確的錯誤。 對於pyodbc，我專門嘗試捕獲一個稱為“ pyodbc.Error”的錯誤，但當前所有錯誤都會導致測試通過。

我希望測試失敗，除非引發的錯誤是except子句中指定的錯誤。 我不想進行“全部捕獲”嘗試。

def get_database():
    try:
        conn = pyodbc.connect(
            r'Driver={Microsoft Access Driver (*.mdb, *.accdb)};'
            r'DBQ=M:\Path\To\Database\My_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

這是一個工作示例，似乎捕獲了非pyodbc.Error錯誤。 您能說明您要做什么嗎？

import pyodbc
import unittest
import mock

def get_database():
    try:
        conn = pyodbc.connect(
            r'Driver={Microsoft Access Driver (*.mdb, *.accdb)};'
            r'DBQ=M:\Path\To\Database\My_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()

帶輸出

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