测试¶

感谢 Starlette，测试FastAPI 应用轻松又愉快。

它基于 HTTPX，而HTTPX又是基于Requests设计的，所以很相似且易懂。

有了它，你可以直接与FastAPI一起使用 pytest。

使用 `TestClient`¶

信息

要使用 TestClient，先要安装 httpx.

例：pip install httpx.

导入 TestClient.

通过传入你的FastAPI应用创建一个 TestClient 。

创建名字以 test_ 开头的函数（这是标准的 pytest 约定）。

像使用 httpx 那样使用 TestClient 对象。

为你需要检查的地方用标准的Python表达式写个简单的 assert 语句（重申，标准的pytest）。

from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}


client = TestClient(app)


def test_read_main():
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"msg": "Hello World"}

提示

注意测试函数是普通的 def，不是 async def。

还有client的调用也是普通的调用，不是用 await。

这让你可以直接使用 pytest 而不会遇到麻烦。

技术细节

你也可以用 from starlette.testclient import TestClient。

FastAPI 提供了和 starlette.testclient 一样的 fastapi.testclient，只是为了方便开发者。但它直接来自Starlette。

提示

除了发送请求之外，如果你还想测试时在FastAPI应用中调用 async 函数（例如异步数据库函数），可以在高级教程中看下 Async Tests 。

分离测试¶

在实际应用中，你可能会把你的测试放在另一个文件里。

您的FastAPI应用程序也可能由一些文件/模块组成等等。

FastAPI app 文件¶

假设你有一个像更大的应用中所描述的文件结构:

.
├── app
│   ├── __init__.py
│   └── main.py

在 main.py 文件中你有一个 FastAPI app:

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}

测试文件¶

然后你会有一个包含测试的文件 test_main.py 。app可以像Python包那样存在（一样是目录，但有个 __init__.py 文件）：

.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py

因为这文件在同一个包中，所以你可以通过相对导入从 main 模块（main.py）导入app对象：

from fastapi.testclient import TestClient

from .main import app

client = TestClient(app)


def test_read_main():
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"msg": "Hello World"}

...然后测试代码和之前一样的。

测试：扩展示例¶

现在让我们扩展这个例子，并添加更多细节，看下如何测试不同部分。

扩展后的 FastAPI app 文件¶

让我们继续之前的文件结构：

.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py

假设现在包含FastAPI app的文件 main.py 有些其他路径操作。

有个 GET 操作会返回错误。

有个 POST 操作会返回一些错误。

所有路径操作 都需要一个X-Token 头。

Python 3.10+Python 3.9+Python 3.8+Python 3.10+ non-AnnotatedPython 3.8+ non-Annotated

from typing import Annotated

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel

fake_secret_token = "coneofsilence"

fake_db = {
    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: str | None = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item.id in fake_db:
        raise HTTPException(status_code=400, detail="Item already exists")
    fake_db[item.id] = item
    return item

from typing import Annotated, Union

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel

fake_secret_token = "coneofsilence"

fake_db = {
    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item.id in fake_db:
        raise HTTPException(status_code=400, detail="Item already exists")
    fake_db[item.id] = item
    return item

from typing import Union

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel
from typing_extensions import Annotated

fake_secret_token = "coneofsilence"

fake_db = {
    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item.id in fake_db:
        raise HTTPException(status_code=400, detail="Item already exists")
    fake_db[item.id] = item
    return item

Tip

Prefer to use the Annotated version if possible.

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel

fake_secret_token = "coneofsilence"

fake_db = {
    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: str | None = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item.id in fake_db:
        raise HTTPException(status_code=409, detail="Item already exists")
    fake_db[item.id] = item
    return item

Tip

Prefer to use the Annotated version if possible.

from typing import Union

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel

fake_secret_token = "coneofsilence"

fake_db = {
    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: str = Header()):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item.id in fake_db:
        raise HTTPException(status_code=409, detail="Item already exists")
    fake_db[item.id] = item
    return item

扩展后的测试文件¶

然后您可以使用扩展后的测试更新test_main.py：

from fastapi.testclient import TestClient

from .main import app

client = TestClient(app)


def test_read_item():
    response = client.get("/items/foo", headers={"X-Token": "coneofsilence"})
    assert response.status_code == 200
    assert response.json() == {
        "id": "foo",
        "title": "Foo",
        "description": "There goes my hero",
    }


def test_read_item_bad_token():
    response = client.get("/items/foo", headers={"X-Token": "hailhydra"})
    assert response.status_code == 400
    assert response.json() == {"detail": "Invalid X-Token header"}


def test_read_nonexistent_item():
    response = client.get("/items/baz", headers={"X-Token": "coneofsilence"})
    assert response.status_code == 404
    assert response.json() == {"detail": "Item not found"}


def test_create_item():
    response = client.post(
        "/items/",
        headers={"X-Token": "coneofsilence"},
        json={"id": "foobar", "title": "Foo Bar", "description": "The Foo Barters"},
    )
    assert response.status_code == 200
    assert response.json() == {
        "id": "foobar",
        "title": "Foo Bar",
        "description": "The Foo Barters",
    }


def test_create_item_bad_token():
    response = client.post(
        "/items/",
        headers={"X-Token": "hailhydra"},
        json={"id": "bazz", "title": "Bazz", "description": "Drop the bazz"},
    )
    assert response.status_code == 400
    assert response.json() == {"detail": "Invalid X-Token header"}


def test_create_existing_item():
    response = client.post(
        "/items/",
        headers={"X-Token": "coneofsilence"},
        json={
            "id": "foo",
            "title": "The Foo ID Stealers",
            "description": "There goes my stealer",
        },
    )
    assert response.status_code == 409
    assert response.json() == {"detail": "Item already exists"}

每当你需要客户端在请求中传递信息，但你不知道如何传递时，你可以通过搜索（谷歌）如何用 httpx做，或者是用 requests 做，毕竟HTTPX的设计是基于Requests的设计的。

接着只需在测试中同样操作。

示例：

传一个路径或查询参数，添加到URL上。
传一个JSON体，传一个Python对象(例如一个dict)到参数 json。
如果你需要发送 Form Data 而不是 JSON，使用 data 参数。
要发送 headers，传 dict 给 headers 参数。
对于 cookies，传 dict 给 cookies 参数。

关于如何传数据给后端的更多信息 (使用httpx 或 TestClient)，请查阅 HTTPX 文档.

信息

注意 TestClient 接收可以被转化为JSON的数据，而不是Pydantic模型。

如果你在测试中有一个Pydantic模型，并且你想在测试时发送它的数据给应用，你可以使用在JSON Compatible Encoder介绍的jsonable_encoder 。

运行起来¶

之后，你只需要安装 pytest:

$ pip install pytest

---> 100%

他会自动检测文件和测试，执行测试，然后向你报告结果。

执行测试：

$ pytest

================ test session starts ================
platform linux -- Python 3.6.9, pytest-5.3.5, py-1.8.1, pluggy-0.13.1
rootdir: /home/user/code/superawesome-cli/app
plugins: forked-1.1.3, xdist-1.31.0, cov-2.8.1
collected 6 items

---> 100%

test_main.py <span style="color: green; white-space: pre;">......                            [100%]</span>

<span style="color: green;">================= 1 passed in 0.03s =================</span>

测试¶

使用 TestClient¶