```

/// note | "Technical Details"

You could also use `from starlette.responses import Response` or `from starlette.responses import JSONResponse`.

**FastAPI** provides the same `starlette.responses` as `fastapi.responses` just as a convenience for you, the developer. But most of the available responses come directly from Starlette.

from fastapi import APIRouter, FastAPI
from fastapi.testclient import TestClient
from pydantic import BaseModel


class ResponseModel(BaseModel):
    message: str


app = FastAPI()
router = APIRouter()


@router.get("/a", responses={501: {"description": "Error 1"}})
async def a():
    return "a"


@router.get(
    "/b",
    responses={
        502: {"description": "Error 2"},

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.dependencies.tutorial001 import app

client = TestClient(app)


@pytest.mark.parametrize(
    "path,expected_status,expected_response",
    [
        ("/items", 200, {"q": None, "skip": 0, "limit": 100}),
        ("/items?q=foo", 200, {"q": "foo", "skip": 0, "limit": 100}),

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient


@pytest.fixture(name="client")
def get_client():
    from docs_src.schema_extra_example.tutorial005_an import app

    client = TestClient(app)
    return client


def test_post_body_example(client: TestClient):
    response = client.put(
        "/items/5",
        json={
            "name": "Foo",

    assertThat(request.requestUrl.toString()).isEqualTo("http://127.0.0.1/")
  }

  @Test fun testHostname() {
    val headers = headersOf("Host", "host-from-header.com")
    val socket =
      FakeSocket(
        localAddress =
          InetAddress.getByAddress(
            "host-from-address.com",
            byteArrayOf(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1),
          ),
        localPort = 80,
      )

```

////

And all of them can use `yield`.

In this case `dependency_c`, to execute its exit code, needs the value from `dependency_b` (here named `dep_b`) to still be available.

And, in turn, `dependency_b` needs the value from `dependency_a` (here named `dep_a`) to be available for its exit code.

//// tab | Python 3.9+

```Python hl_lines="18-19  26-27"

import pytest
from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI()


@app.get("/a", responses={"hello": {"description": "Not a valid additional response"}})
async def a():
    pass  # pragma: no cover


openapi_schema = {
    "openapi": "3.1.0",
    "info": {"title": "FastAPI", "version": "0.1.0"},
    "paths": {
        "/a": {
            "get": {
                "responses": {

from typing import Annotated

from fastapi import Depends, FastAPI, HTTPException

app = FastAPI()


data = {
    "plumbus": {"description": "Freshly pickled plumbus", "owner": "Morty"},
    "portal-gun": {"description": "Gun to create portals", "owner": "Rick"},
}


class OwnerError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except OwnerError as e:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: set[str] = set()


@app.post(
    "/items/",
    response_model=Item,
    summary="Create an item",
    response_description="The created item",
)
async def create_item(item: Item):
    """

from fastapi import FastAPI
from fastapi.testclient import TestClient

app = FastAPI(swagger_ui_oauth2_redirect_url=None)


@app.get("/items/")
async def read_items():
    return {"id": "foo"}


client = TestClient(app)


def test_swagger_ui():
    response = client.get("/docs")
    assert response.status_code == 200, response.text
    assert response.headers["content-type"] == "text/html; charset=utf-8"