from fastapi import FastAPI, Path

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(q: str, item_id: int = Path(title="The ID of the item to get")):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

///

/// tip

If you want to call `async` functions in your tests apart from sending requests to your FastAPI application (e.g. asynchronous database functions), have a look at the [Async Tests](../advanced/async-tests.md){.internal-link target=_blank} in the advanced tutorial.

///

## Separating tests { #separating-tests }

# Without aliases


@app.post("/required-bytes", operation_id="required_bytes")
async def read_required_bytes(p: Annotated[bytes, File()]):
    return {"file_size": len(p)}


@app.post("/required-uploadfile", operation_id="required_uploadfile")
async def read_required_uploadfile(p: Annotated[UploadFile, File()]):
    return {"file_size": p.size}


@pytest.mark.parametrize(

app = FastAPI()


class UserIn(BaseModel):
    username: str
    password: str
    email: EmailStr
    full_name: str | None = None


# Don't do this in production!
@app.post("/user/")
async def create_user(user: UserIn) -> UserIn:

class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None


app = FastAPI()


@app.post("/items/")
async def create_item(item: Item):

from fastapi import FastAPI, Path

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    *, item_id: int = Path(title="The ID of the item to get", ge=1), q: str
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

from typing import Annotated, Union

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[Union[str, None], Query(max_length=50)] = None):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

app = FastAPI()


class BaseUser(BaseModel):
    username: str
    email: EmailStr
    full_name: Union[str, None] = None


class UserIn(BaseUser):
    password: str


@app.post("/user/")
async def create_user(user: UserIn) -> BaseUser:

app = FastAPI()


class Cookies(BaseModel):
    model_config = {"extra": "forbid"}

    session_id: str
    fatebook_tracker: str | None = None
    googall_tracker: str | None = None


@app.get("/items/")
async def read_items(cookies: Annotated[Cookies, Cookie()]):

class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header(convert_underscores=False)):