解决Python单元测试中Mock异常方法调用计数为零的问题

import json

import logging

# 假设这些是外部库的类和异常

class GoogleCloudError(Exception):

    pass

class Blob:

    def __init__(self, name, bucket):

        self.name = name

        self.bucket = bucket

    def upload_from_string(self, data, content_type):

        """模拟上传文件到云存储"""

        # 实际实现可能包含与云服务交互的逻辑

        print(f"Uploading {self.name} to {self.bucket} with data: {data}")

        # 这里为了模拟，不实际上传

class UploadService:

    def __init__(self, bucket_name):

        self.bucket_name = bucket_name

    def upload(self, name, data):

        try:

            # 实例化 Blob 对象

            gcs_blob = Blob(name, self.bucket_name)

            # 调用实例方法

            gcs_blob.upload_from_string(data=json.dumps(data), content_type="application/json")

            return "Upload successful"

        except GoogleCloudError as e:

            logging.exception(f"Error uploading file {name} to {self.bucket_name}")

            return f"Upload failed: {e}"

import unittest

from unittest.mock import patch, Mock

from upload_service import UploadService, Blob, GoogleCloudError

class TestUploadService(unittest.TestCase):

    def test_upload_failure(self):

        us = UploadService("my-test-bucket")

        test_data = {"key": "value"}

        test_name = "test-file.json"

        with patch("upload_service.Blob") as MockedBlobClass:

            # 获取模拟的 Blob 实例

            gcs_blob_instance = MockedBlobClass.return_value

            # 设置实例方法在调用时抛出异常

            gcs_blob_instance.upload_from_string.side_effect = GoogleCloudError("Google Cloud upload failed")

            # 调用待测试的方法

            result = us.upload(test_name, test_data)

            # 断言异常被处理

            self.assertIn("Upload failed", result)

            # 错误的断言：尝试在 MockedBlobClass 上检查 call_count

            # 预期这里是1，但实际是0

            self.assertEqual(1, MockedBlobClass.upload_from_string.call_count)

AssertionError: 1 != 0

Expected :1

Actual   :0

import unittest

from unittest.mock import patch, Mock

from upload_service import UploadService, Blob, GoogleCloudError

class TestUploadService(unittest.TestCase):

    def test_upload_failure_corrected(self):

        us = UploadService("my-test-bucket")

        test_data = {"key": "value"}

        test_name = "test-file.json"

        with patch("upload_service.Blob") as MockedBlobClass:

            # 获取模拟的 Blob 实例

            gcs_blob_instance = MockedBlobClass.return_value

            # 设置实例方法在调用时抛出异常

            gcs_blob_instance.upload_from_string.side_effect = GoogleCloudError("Google Cloud upload failed")

            # 调用待测试的方法

            result = us.upload(test_name, test_data)

            # 断言异常被处理

            self.assertIn("Upload failed", result)

            # 正确的断言：在模拟的实例方法上检查 call_count

            self.assertEqual(1, gcs_blob_instance.upload_from_string.call_count)

            # 也可以通过 MockedBlobClass().upload_from_string 来访问，效果相同

            # self.assertEqual(1, MockedBlobClass().upload_from_string.call_count)