Python AWS Lambda 的单元测试：导入模块之前的模拟函数

Question

我正在尝试为使用 python 3.9 编写的 aws lambda 函数编写单元测试。我尝试了不同的方法来模拟调用 S3 的 get_object 函数。我只想关注 calculate 方法，以验证我是否获得了正确的计算结果。

当我尝试运行以下方法时，我收到有关 boto3

的凭据错误

python -m unittest tests/app-test.py
...
botocore.exceptions.NoCredentialsError: Unable to locate credentials

有没有办法从 app.py 导入 calculate 方法并模拟调用 get_object fn？

functions:
- __init__.py
- app.py
tests:
- __init__.py
- app-test.py

lambda 函数app.py:

import json
import boto3

def get_object():
    s3 = boto3.client('s3')
    response = s3.get_object(Bucket='mybucket', Key='object.json')
    content = response['Body'].read().decode('utf-8')
    return json.loads(content)


stops = get_object()


def lambda_handler(event, context): 
    params = event['queryStringParameters']
    a = int(params['a'])
    b = int(params['b'])
   
    result = calculate(a, b)
    return {
        'statusCode': 200,
        'body': json.dumps(result)
    }


def calculate(a, b):
    return a + b

单元测试app-test.py:

import unittest
from unittest import mock

with mock.patch('functions.app.get_object', return_value={}):
    from functions.app import calculate

class TestCalculation(unittest.TestCase):
   def test_should_return_correct_calculation(self):
     # when
     result = calculate(1, 2)

     # then
     self.assertEqual(3, result)

Answer 1

我能够解决这个问题。最大的障碍是在 app.py 中嘲笑 boto3。我通过在导入之前模拟整个 boto3 模块来做到这一点。这是 app-test.py

的代码

import sys
from io import BytesIO
from json import dumps
from unittest import TestCase, main
from unittest.mock import Mock
from botocore.stub import Stubber
from botocore.session import get_session
from botocore.response import StreamingBody


# prepare mocks for boto3
stubbed_client = get_session().create_client('s3')
stubber = Stubber(stubbed_client)

# mock response from S3
body_encoded = dumps({'name': 'hello world'}).encode()
body = StreamingBody(BytesIO(body_encoded), len(body_encoded))
stubbed.add_response('get_object', {'Body': body})

stubber.activate()

# add mocks to the real module
sys.modules['boto3'] = Mock()
sys.modules['boto3'].client = Mock(return_value=stubbed_client)


# Import the module that will be tested
# boto3 should be mocked in the app.py
from functions.app import calculate


class TestCalculation(TestCase):
   def test_should_return_correct_calculation(self):
     # when
     result = calculate(1, 2)

     # then
     self.assertEqual(3, result)

Python AWS Lambda 的单元测试：导入模块之前的模拟函数

Unit test for Python AWS Lambda: mock function before module is imported

python

unit-testing

aws-lambda

python-unittest