如何用requests-mock或其他库测试Python requests的各类场景及SSL证书故障？

基础请求场景测试（以requests-mock为主） #

• 服务器不可达：这种情况是连不上服务器，不用requests-mock，直接用unittest.mock模拟requests.get抛出requests.exceptions.ConnectionError即可：

  from unittest.mock import patch
  import requests
  
  def test_server_unreachable():
      with patch('requests.get') as mock_get:
          mock_get.side_effect = requests.exceptions.ConnectionError
          try:
              requests.get('http://unreachable.server')
          except requests.exceptions.ConnectionError:
              assert True
          else:
              assert False
  

• 服务器可达但目标服务不可用：用requests-mock模拟返回5xx状态码（比如503），模拟服务不可用的情况：

  import requests_mock
  import requests
  
  def test_service_unavailable():
      with requests_mock.Mocker() as m:
          m.get('http://available.server/unavailable', status_code=503)
          response = requests.get('http://available.server/unavailable')
          assert response.status_code == 503
  

• 请求调用失败：模拟返回4xx状态码（比如400、404），或者直接抛出请求异常（比如超时）：

  import requests_mock
  import requests
  
  def test_request_failure():
      # 模拟400错误
      with requests_mock.Mocker() as m:
          m.get('http://api.server/bad-request', status_code=400)
          response = requests.get('http://api.server/bad-request')
          assert response.status_code == 400
      
      # 模拟超时异常
      with requests_mock.Mocker() as m:
          m.get('http://api.server/timeout', exc=requests.exceptions.Timeout)
          try:
              requests.get('http://api.server/timeout')
          except requests.exceptions.Timeout:
              assert True
  

• 请求调用成功：用requests-mock模拟返回200状态码和正常响应内容：

  import requests_mock
  import requests
  
  def test_request_success():
      with requests_mock.Mocker() as m:
          m.get('http://api.server/success', json={'data': 'ok'}, status_code=200)
          response = requests.get('http://api.server/success')
          assert response.status_code == 200
          assert response.json() == {'data': 'ok'}
  

SSL证书场景测试（结合requests参数+unittest.mock/自定义证书文件） #

• 证书有效：正常请求时指定有效证书文件即可，或者在mock场景下默认不会触发真实SSL校验，如果要模拟真实校验逻辑，可使用有效证书文件测试：

  import requests
  
  def test_valid_ssl_certificate():
      # 假设已有有效证书文件valid_cert.pem
      try:
          response = requests.get('https://valid.server', verify='valid_cert.pem')
          assert response.status_code == 200
      except requests.exceptions.SSLError:
          assert False
  

• 证书过期/证书链缺失/无效：有两种实现方式：
  1. 使用真实的过期/无效证书文件，请求时指定verify参数为该文件，会触发SSLError：

     import requests
     
     def test_invalid_ssl_certificate():
         # 假设已有过期证书文件expired_cert.pem
         try:
             requests.get('https://expired.server', verify='expired_cert.pem')
         except requests.exceptions.SSLError:
             assert True
         else:
             assert False
     

  2. 用unittest.mock模拟请求过程抛出SSLError，无需真实证书文件：

     from unittest.mock import patch
     import requests
     from requests.exceptions import SSLError
     
     def test_ssl_error_mock():
         with patch('requests.adapters.HTTPAdapter.send') as mock_send:
             mock_send.side_effect = SSLError("证书无效/过期/链缺失")
             try:
                 requests.get('https://invalid.server')
             except SSLError:
                 assert True
             else:
                 assert False
     

内容的提问来源于stack exchange，提问作者nikoladsp