Python自定义异常的单元测试策略与常见陷阱

import inspect

class ApiException(Exception):
  """
  自定义API异常类，封装HTTP错误码、消息和调用位置信息。
  """
  def __init__(self, response) -> None:
    self.http_code = response.status_code
    self.message = response.text.replace("\n", " ")
    # 获取异常抛出时的调用栈信息
    self.caller = inspect.getouterframes(inspect.currentframe(), 2)[1]
    self.caller_file = self.caller[1]
    self.caller_line = self.caller[2]

  def __str__(self) -> str:
    return f"Error code {self.http_code} with message '{self.message}' in file {self.caller_file} line {self.caller_line}"

# 模拟API响应对象
class MockResponse:
    def __init__(self, ok, status_code, text):
        self.ok = ok
        self.status_code = status_code
        self.text = text

# 模拟API调用逻辑
def call_gitlab_api(response: MockResponse):
    if response.ok:
        # 假设这里返回一个MergeRequest对象
        return {"status": "success"}
    else:
        raise ApiException(response=response)

# 假设这是单元测试中的一段代码
try:
    call_gitlab_api(MockResponse(ok=False, status_code=401, text="Unauthorized"))
    assert False # 如果没有抛出异常，则测试失败
except Exception as err:
    # TestLogger.info(type(err)) # 打印结果可能是 <class 'APIs.api_exceptions.ApiException'>
    # TestLogger.info(isinstance(err, ApiException)) # 却可能打印 False
    assert isinstance(err, ApiException) # 导致测试失败

import unittest

# 假设ApiException和call_gitlab_api已定义在可导入的模块中
# from your_module import ApiException, call_gitlab_api, MockResponse

class TestApiExceptionHandling(unittest.TestCase):
  def test_api_call_raises_api_exception(self):
    """
    测试当API响应不成功时，是否抛出ApiException。
    """
    mock_response = MockResponse(ok=False, status_code=401, text="Unauthorized access")

    try:
      call_gitlab_api(mock_response)
      self.fail("ApiException was not raised as expected.") # 如果没有抛出异常，强制测试失败
    except ApiException as err:
      # 验证异常类型已经通过except子句完成
      # 进一步验证异常的属性，确保其内容正确
      self.assertEqual(err.http_code, 401)
      self.assertIn("Unauthorized access", err.message)
      # 也可以验证其他属性，如caller_file, caller_line等
    except Exception as err:
      self.fail(f"Caught an unexpected exception type: {type(err).__name__}")

  def test_api_call_succeeds(self):
    """
    测试当API响应成功时，不抛出异常并返回正确结果。
    """
    mock_response = MockResponse(ok=True, status_code=200, text='{"status": "success"}')
    result = call_gitlab_api(mock_response)
    self.assertEqual(result, {"status": "success"})

# 运行测试
# if __name__ == '__main__':
#     unittest.main()

import unittest

class TestApiExceptionHandlingWithIsinstance(unittest.TestCase):
  def test_api_call_raises_api_exception_with_isinstance(self):
    """
    测试当API响应不成功时，使用isinstance验证是否抛出ApiException。
    """
    mock_response = MockResponse(ok=False, status_code=403, text="Forbidden")

    try:
      call_gitlab_api(mock_response)
      self.fail("ApiException was not raised as expected.")
    except Exception as err: # 捕获所有异常
      self.assertTrue(isinstance(err, ApiException), f"Expected ApiException, but got {type(err).__name__}")
      self.assertEqual(err.http_code, 403)
      self.assertIn("Forbidden", err.message)

# 运行测试
# if __name__ == '__main__':
#     unittest.main()

import pytest

# 假设ApiException和call_gitlab_api已定义在可导入的模块中

def test_api_call_raises_api_exception_with_pytest_raises():
  """
  使用pytest.raises测试当API响应不成功时，是否抛出ApiException。
  """
  mock_response = MockResponse(ok=False, status_code=500, text="Internal Server Error")

  with pytest.raises(ApiException) as excinfo:
    call_gitlab_api(mock_response)

  # excinfo对象包含了捕获到的异常信息
  exception = excinfo.value # 获取实际的异常实例

  assert exception.http_code == 500
  assert "Internal Server Error" in exception.message
  assert "ApiException" in str(exception.__class__) # 验证类名
  # 可以进一步验证异常的字符串表示
  assert "Error code 500 with message 'Internal Server Error'" in str(exception)

def test_api_call_raises_api_exception_with_message_check():
  """
  使用pytest.raises并直接检查异常消息。
  """
  mock_response = MockResponse(ok=False, status_code=400, text="Bad Request")

  # 可以直接在pytest.raises中检查异常类型和部分匹配的消息
  with pytest.raises(ApiException, match="Bad Request") as excinfo:
    call_gitlab_api(mock_response)

  assert excinfo.value.http_code == 400

def test_api_call_succeeds_with_pytest():
  """
  测试当API响应成功时，不抛出异常并返回正确结果（pytest风格）。
  """
  mock_response = MockResponse(ok=True, status_code=200, text='{"status": "success"}')
  result = call_gitlab_api(mock_response)
  assert result == {"status": "success"}