测试依赖项¶
测试时覆盖依赖项¶
有些场景下，您可能需要在测试时覆盖依赖项。
即不希望运行原有依赖项（及其子依赖项）。
反之，要在测试期间（或只是为某些特定测试）提供只用于测试的依赖项，并使用此依赖项的值替换原有依赖项的值。
用例：外部服务¶
常见实例是调用外部第三方身份验证应用。
向第三方应用发送令牌，然后返回经验证的用户。
但第三方服务商处理每次请求都可能会收费，并且耗时通常也比调用写死的模拟测试用户更长。
一般只要测试一次外部验证应用就够了，不必每次测试都去调用。
此时，最好覆盖调用外部验证应用的依赖项，使用返回模拟测试用户的自定义依赖项就可以了。
使用 app.dependency_overrides 属性¶
对于这些用例，FastAPI 应用支持 app.dependency_overrides 属性，该属性就是字典。
要在测试时覆盖原有依赖项，这个字典的键应当是原依赖项（函数），值是覆盖依赖项（另一个函数）。
这样一来，FastAPI 就会调用覆盖依赖项，不再调用原依赖项。
from typing import Annotated
from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient
app = FastAPI()
async def common_parameters(q: str | None = None, skip: int = 0, limit: int = 100):
return {"q": q, "skip": skip, "limit": limit}
@app.get("/items/")
async def read_items(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Items!", "params": commons}
@app.get("/users/")
async def read_users(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Users!", "params": commons}
client = TestClient(app)
async def override_dependency(q: str | None = None):
return {"q": q, "skip": 5, "limit": 10}
app.dependency_overrides[common_parameters] = override_dependency
def test_override_in_items():
response = client.get("/items/")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": None, "skip": 5, "limit": 10},
}
def test_override_in_items_with_q():
response = client.get("/items/?q=foo")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
def test_override_in_items_with_params():
response = client.get("/items/?q=foo&skip=100&limit=200")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
🤓 Other versions and variants
from typing import Annotated, Union
from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient
app = FastAPI()
async def common_parameters(
q: Union[str, None] = None, skip: int = 0, limit: int = 100
):
return {"q": q, "skip": skip, "limit": limit}
@app.get("/items/")
async def read_items(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Items!", "params": commons}
@app.get("/users/")
async def read_users(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Users!", "params": commons}
client = TestClient(app)
async def override_dependency(q: Union[str, None] = None):
return {"q": q, "skip": 5, "limit": 10}
app.dependency_overrides[common_parameters] = override_dependency
def test_override_in_items():
response = client.get("/items/")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": None, "skip": 5, "limit": 10},
}
def test_override_in_items_with_q():
response = client.get("/items/?q=foo")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
def test_override_in_items_with_params():
response = client.get("/items/?q=foo&skip=100&limit=200")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
from typing import Union
from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient
from typing_extensions import Annotated
app = FastAPI()
async def common_parameters(
q: Union[str, None] = None, skip: int = 0, limit: int = 100
):
return {"q": q, "skip": skip, "limit": limit}
@app.get("/items/")
async def read_items(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Items!", "params": commons}
@app.get("/users/")
async def read_users(commons: Annotated[dict, Depends(common_parameters)]):
return {"message": "Hello Users!", "params": commons}
client = TestClient(app)
async def override_dependency(q: Union[str, None] = None):
return {"q": q, "skip": 5, "limit": 10}
app.dependency_overrides[common_parameters] = override_dependency
def test_override_in_items():
response = client.get("/items/")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": None, "skip": 5, "limit": 10},
}
def test_override_in_items_with_q():
response = client.get("/items/?q=foo")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
def test_override_in_items_with_params():
response = client.get("/items/?q=foo&skip=100&limit=200")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
Tip
Prefer to use the Annotated version if possible.
from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient
app = FastAPI()
async def common_parameters(q: str | None = None, skip: int = 0, limit: int = 100):
return {"q": q, "skip": skip, "limit": limit}
@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
return {"message": "Hello Items!", "params": commons}
@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):
return {"message": "Hello Users!", "params": commons}
client = TestClient(app)
async def override_dependency(q: str | None = None):
return {"q": q, "skip": 5, "limit": 10}
app.dependency_overrides[common_parameters] = override_dependency
def test_override_in_items():
response = client.get("/items/")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": None, "skip": 5, "limit": 10},
}
def test_override_in_items_with_q():
response = client.get("/items/?q=foo")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
def test_override_in_items_with_params():
response = client.get("/items/?q=foo&skip=100&limit=200")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
Tip
Prefer to use the Annotated version if possible.
from typing import Union
from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient
app = FastAPI()
async def common_parameters(
q: Union[str, None] = None, skip: int = 0, limit: int = 100
):
return {"q": q, "skip": skip, "limit": limit}
@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
return {"message": "Hello Items!", "params": commons}
@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):
return {"message": "Hello Users!", "params": commons}
client = TestClient(app)
async def override_dependency(q: Union[str, None] = None):
return {"q": q, "skip": 5, "limit": 10}
app.dependency_overrides[common_parameters] = override_dependency
def test_override_in_items():
response = client.get("/items/")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": None, "skip": 5, "limit": 10},
}
def test_override_in_items_with_q():
response = client.get("/items/?q=foo")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
def test_override_in_items_with_params():
response = client.get("/items/?q=foo&skip=100&limit=200")
assert response.status_code == 200
assert response.json() == {
"message": "Hello Items!",
"params": {"q": "foo", "skip": 5, "limit": 10},
}
提示
FastAPI 应用中的任何位置都可以实现覆盖依赖项。
原依赖项可用于路径操作函数、路径操作装饰器（不需要返回值时）、.include_router() 调用等。
FastAPI 可以覆盖这些位置的依赖项。
然后，使用 app.dependency_overrides 把覆盖依赖项重置为空字典：
app.dependency_overrides = {}
提示
如果只在某些测试时覆盖依赖项，您可以在测试开始时（在测试函数内）设置覆盖依赖项，并在结束时（在测试函数结尾）重置覆盖依赖项。