我正在尝试检查特定模型是否用作 FastAPI 路由的输入解析器。但是，我不确定如何修补(或监视)它。
我有以下文件结构:
.
└── roo
├── __init__.py
├── main.py
└── test_demo.py
主要.py:
from fastapi import FastAPI
from pydantic import BaseModel
app = FastAPI()
class ItemModel(BaseModel):
name: str
@app.post("/")
async def read_main(item: ItemModel):
return {"msg": f"Item: {item.name}"}
test_demo.py:
from fastapi.testclient import TestClient
from unittest.mock import patch
from roo.main import app, ItemModel
client = TestClient(app)
def test_can_creating_new_item_users_proper_validation_model():
with patch('roo.main.ItemModel', wraps=ItemModel) as patched_model:
response = client.post("/", json={'name': 'good'})
assert response.status_code == 200
assert response.json() == {"msg": "Item: good"}
assert patched_model.called
但是，patched_model 从未被调用(其他断言通过)。我不想更改功能或替换 main.py 中的 ItemModel，我只是想检查它是否被使用。
最佳答案
我的第一个方法是包装 read_main 方法并检查传递给函数的 item 确实是 项目模型。但由于 FastAPI 端点的准备和存储方式，这是一种死胡同的方法:FastAPI 将端点函数对象的副本存储在列表中:(请参阅 fastapi/routing.py)，然后在请求时评估要调用的端点。
from roo.main import app
def test_read_main():
assert 'read_main' in [r.endpoint.__name__ for r in app.routes]
# check that read_main was called *and* received an ItemModel instance?
我的第二种方法涉及监视或“破坏”ItemModel 的初始化，这样如果端点确实确实使用该模型，那么“破坏” ItemModel 会导致命中该端点的请求失败。我们通过利用以下事实来“破坏”ItemModel:(1) FastAPI 在请求-响应周期中调用模型的 __init__，以及 (2) 422 错误当端点无法正确序列化模型时，默认情况下会传播响应:
class ItemModel(BaseModel):
name: str
def __init__(__pydantic_self__, **data: Any) -> None:
print("Make a POST request and confirm that this is printed out")
super().__init__(**data)
因此在测试中，只需模拟 __init__ 方法:
- pytest 示例
import pytest from fastapi.testclient import TestClient from roo.main import app, ItemModel def test_read_main(monkeypatch: pytest.MonkeyPatch): client = TestClient(app) def broken_init(self, **data): pass # `name` and other fields won't be set monkeypatch.setattr(ItemModel, '__init__', broken_init) with pytest.raises(AttributeError) as exc: client.post("/", json={'name': 'good'}) assert 422 == response.status_code assert "'ItemModel' object has no attribute" in str(exc.value) - pytest + pytest-mock 示例的
mocker.spyfrom fastapi.testclient import TestClient from pytest_mock import MockerFixture from roo.main import app, ItemModel def test_read_main(mocker: MockerFixture): client = TestClient(app) spy = mocker.spy(ItemModel, '__init__') client.post("/", json={'name': 'good'}) spy.assert_called() spy.assert_called_with(**{'name': 'good'}) - 单元测试示例
from fastapi.testclient import TestClient from roo.main import app, ItemModel from unittest.mock import patch def test_read_main(): client = TestClient(app) # Wrapping __init__ like this isn't really correct, but serves the purpose with patch.object(ItemModel, '__init__', wraps=ItemModel.__init__) as mocked_init: response = client.post("/", json={'name': 'good'}) assert 422 == response.status_code mocked_init.assert_called() mocked_init.assert_called_with(**{'name': 'good'})
再次，测试检查端点是否在序列化为 ItemModel 或访问 item.name 时失败，只有当端点是 时才会发生确实使用ItemModel。
如果将端点从 item: ItemModel 修改为 item: OtherModel:
class OtherModel(BaseModel):
name: str
class ItemModel(BaseModel):
name: str
@app.post("/")
async def read_main(item: OtherModel): # <----
return {"msg": f"Item: {item.name}"}
然后运行测试现在应该会失败，因为端点现在正在创建错误的对象:
def test_read_main(mocker: MockerFixture):
client = TestClient(app)
spy = mocker.spy(ItemModel, '__init__')
client.post("/", json={'name': 'good'})
> spy.assert_called()
E AssertionError: Expected '__init__' to have been called.
test_demo_spy.py:11: AssertionError
with pytest.raises(AttributeError) as exc:
response = client.post("/", json={'name': 'good'})
> assert 422 == response.status_code
E assert 422 == 200
E +422
E -200
test_demo_pytest.py:15: AssertionError
422 == 200 的断言错误有点令人困惑，但它基本上意味着即使我们“破坏”了 ItemModel，我们仍然得到 200/OK 响应..这意味着 ItemModel 未被使用。
同样，如果您首先修改了测试并模拟了 OtherModel 的 __init__ 而不是 ItemModel，那么在不修改的情况下运行测试端点将导致类似的失败测试:
def test_read_main(mocker: MockerFixture):
client = TestClient(app)
spy = mocker.spy(OtherModel, '__init__')
client.post("/", json={'name': 'good'})
> spy.assert_called()
E AssertionError: Expected '__init__' to have been called.
def test_read_main():
client = TestClient(app)
with patch.object(OtherModel, '__init__', wraps=OtherModel.__init__) as mocked_init:
response = client.post("/", json={'name': 'good'})
# assert 422 == response.status_code
> mocked_init.assert_called()
E AssertionError: Expected '__init__' to have been called.
这里的断言不那么令人困惑，因为它说我们预计端点将调用 OtherModel 的 __init__，但它没有被调用。它应该在修改端点以使用 item: OtherModel 后通过。
最后要注意的是，由于我们正在操纵 __init__，因此它可能导致“快乐路径”失败，因此现在应该单独对其进行测试。确保撤消/还原模拟和补丁:
- pytest 示例
def test_read_main(monkeypatch: pytest.MonkeyPatch): client = TestClient(app) def broken_init(self, **data): pass # Are we really using ItemModel? monkeypatch.setattr(ItemModel, '__init__', broken_init) with pytest.raises(AttributeError) as exc: response = client.post("/", json={'name': 'good'}) assert 422 == response.status_code assert "'ItemModel' object has no attribute" in str(exc.value) # Okay, really using ItemModel. Does it work correctly? monkeypatch.undo() response = client.post("/", json={'name': 'good'}) assert response.status_code == 200 assert response.json() == {"msg": "Item: good"} - pytest + pytest-mock 示例的
mocker.spyfrom pytest_mock import MockerFixture from fastapi.testclient import TestClient from roo.main import app, ItemModel def test_read_main(mocker: MockerFixture): client = TestClient(app) # Are we really using ItemModel? spy = mocker.spy(ItemModel, '__init__') client.post("/", json={'name': 'good'}) spy.assert_called() spy.assert_called_with(**{'name': 'good'}) # Okay, really using ItemModel. Does it work correctly? mocker.stopall() response = client.post("/", json={'name': 'good'}) assert response.status_code == 200 assert response.json() == {"msg": "Item: good"} - 单元测试示例
def test_read_main(): client = TestClient(app) # Are we really using ItemModel? with patch.object(ItemModel, '__init__', wraps=ItemModel.__init__) as mocked_init: response = client.post("/", json={'name': 'good'}) assert 422 == response.status_code mocked_init.assert_called() mocked_init.assert_called_with(**{'name': 'good'}) # Okay, really using ItemModel. Does it work correctly? response = client.post("/", json={'name': 'good'}) assert response.status_code == 200 assert response.json() == {"msg": "Item: good"}
总而言之，您可能需要考虑检查确切使用的模型是否有用/为什么有用。通常，我只是检查传入的有效请求参数是否返回预期的有效响应，同样，无效请求是否返回错误响应。
关于python - 如何测试模型是否在 FastAPI 路由中使用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/65876503/