如何使用side_effect模拟requests.get().url？附代码测试需求

问题描述 #

我编写了以下Python函数，用于循环调用Swapi的人物列表API，收集所有请求的URL直到API返回非200状态码。同时编写了测试函数，但需要用side_effect模拟requests.get().url和响应状态码来完成离线测试，避免真实调用API：

from http import HTTPStatus
import requests

def consuming_api_swapi_index_page(initial_page: int = 1):
    """Swapi index page."""
    check = HTTPStatus.OK
    results = []
    while check == HTTPStatus.OK:
        response = requests.get(
            f'https://swapi.dev/api/people/?page={initial_page}'
        )
        results.append(url := response.url)
        print(url)
        check = response.status_code
        initial_page += 1
    return results


def test_consuming_api_swapi_index_page() -> None:
    """Test it."""
    values = [
        'https://swapi.dev/api/people/?page=1',
        'https://swapi.dev/api/people/?page=2',
        'https://swapi.dev/api/people/?page=3',
        'https://swapi.dev/api/people/?page=4',
        'https://swapi.dev/api/people/?page=5',
        'https://swapi.dev/api/people/?page=6',
        'https://swapi.dev/api/people/?page=7',
        'https://swapi.dev/api/people/?page=8',
        'https://swapi.dev/api/people/?page=9',
        'https://swapi.dev/api/people/?page=10',
    ]

    assert consuming_api_swapi_index_page() == values

解决方案 #

可以通过unittest.mock的patch装饰器结合side_effect来模拟requests.get的返回值，按顺序返回预设的响应对象，控制每个响应的url和status_code，从而让函数按预期执行并终止循环。

修改后的测试代码 #

from unittest.mock import patch, Mock
from http import HTTPStatus
# 替换为你的函数所在模块名
from your_module import consuming_api_swapi_index_page

def test_consuming_api_swapi_index_page() -> None:
    """Test the API consuming function with mocked requests."""
    expected_urls = [
        'https://swapi.dev/api/people/?page=1',
        'https://swapi.dev/api/people/?page=2',
        'https://swapi.dev/api/people/?page=3',
        'https://swapi.dev/api/people/?page=4',
        'https://swapi.dev/api/people/?page=5',
        'https://swapi.dev/api/people/?page=6',
        'https://swapi.dev/api/people/?page=7',
        'https://swapi.dev/api/people/?page=8',
        'https://swapi.dev/api/people/?page=9',
        'https://swapi.dev/api/people/?page=10',
    ]

    # 构建模拟响应列表：前10个返回200状态和对应URL，最后一个返回404终止循环
    mock_responses = []
    for url in expected_urls:
        resp = Mock()
        resp.url = url
        resp.status_code = HTTPStatus.OK
        mock_responses.append(resp)
    
    # 添加终止循环的非200响应
    final_response = Mock()
    final_response.status_code = HTTPStatus.NOT_FOUND
    mock_responses.append(final_response)

    # 模拟requests.get，按顺序返回预设的响应对象
    with patch('requests.get', side_effect=mock_responses):
        result = consuming_api_swapi_index_page()
        assert result == expected_urls

关键说明 #

1. Mock响应对象：每个Mock()实例模拟requests.get返回的响应对象，设置url属性匹配预期请求地址，status_code控制循环的执行逻辑。
2. side_effect的作用：当requests.get被调用时，会按mock_responses列表的顺序依次返回每个Mock对象。前10次调用返回200状态，函数会将对应URL加入结果列表并继续循环；第11次调用返回404状态，循环终止。
3. 路径正确的patch：patch('requests.get')需要确保路径正确，如果你的函数是在某个模块中导入requests，则需要patch该模块中的requests.get（比如from mymodule import requests的话，要patchmymodule.requests.get）。

内容的提问来源于stack exchange，提问作者britodfbr