python-3.x - Python unittest.mock google storage - 如何实现 exceptions.NotFound 作为副作用

Question

我读过一些tutorials关于在 Python 中进行模拟，但我仍在苦苦挣扎 :-/

例如，我有一个函数包装了对谷歌存储的调用以写入一个 blob。

我想模拟 google.storage.Client().bucket(bucket_name) 方法以针对特定的不存在的存储桶返回 exceptions.NotFound .我正在使用 side_effect 来设置异常(exception)情况

你知道我做错了什么吗？

下面是我尝试过的(我使用了 2 个文件:ma​​in2.py 和 ma​​in2_test.py):

# main2.py
import logging
from google.cloud import storage

def _write_content(bucket_name, blob_name, content):
   storage_client = storage.Client()
   bucket = storage_client.bucket(bucket_name)
   blob = bucket.blob(blob_name)

   try:
        blob.upload_from_string(data=content)
        return True
    except Exception:
        logging.error("Failed to upload blob")
        raise

和

# main2_test.py
import pytest
from unittest.mock import patch
from google.api_core import exceptions
import main2


@patch("main2.storage.Client", autospec=True)
def test_write_content(clientMock):
    bucket_name = "not_existent_bucket"
    clientMock().bucket(bucket_name).side_effect = exceptions.NotFound

    with pytest.raises(exceptions.NotFound):
        main2._write_content(bucket_name, "a_blob_name", '{}')

调用示例

pytest main2_test.py::test_write_content

结果

platform linux -- Python 3.7.7, pytest-5.4.3, py-1.9.0, pluggy-0.13.1
rootdir: /home/user/project, inifile: pytest.ini
plugins: requests-mock-1.8.0
collected 1 item                                                                                                                                                                                     

main2_test.py::test_write_content FAILED                                                                                                                                                       [100%]

============================================================================================== FAILURES ==============================================================================================
_________________________________________________________________________________________ test_write_content _________________________________________________________________________________________

clientMock = <MagicMock name='Client' spec='Client' id='139881522497360'>

    @patch("main2.storage.Client", autospec=True)
    def test_write_content(clientMock):
        bucket_name = "my_bucket"
        clientMock().bucket(bucket_name).side_effect = exceptions.NotFound
    
        with pytest.raises(exceptions.NotFound):
>           main2._write_content(bucket_name, "a_blob_name", '{}')
E           Failed: DID NOT RAISE <class 'google.api_core.exceptions.NotFound'>

main2_test.py:14: Failed
=====================================
FAILED main2_test.py::test_write_content - Failed: DID NOT RAISE <class 'google.api_core.exceptions.NotFound'>
=====================================

Answer 1

您的测试有两个问题:您没有模拟实际引发的方法 (upload_from_string)，并且您正在设置异常 class 而不是 side 异常效果。

以下是可行的:

@patch("main2.storage.Client", autospec=True)
def test_write_content(clientMock):
    blob_mock = clientMock().bucket.return_value.blob.return_value  # split this up for readability
    blob_mock.upload_from_string.side_effect = exceptions.NotFound('testing')  # the exception is created here

    with pytest.raises(exceptions.NotFound):
        main2._write_content("not_existent", "a_blob_name", '{}')

另请注意，为 bucket 调用设置特定参数没有任何效果，因为它是在 mock 上调用的，并且参数会被忽略 - 我将其替换为 return_value，这使这一点更清楚。