Pet = Annotated[
        Union[Annotated[Cat, Tag("cat")], Annotated[Dog, Tag("dog")]],
        Discriminator(get_pet_type),
    ]

    app = FastAPI()

    @app.post("/pet/assignment")
    async def create_pet_assignment(pet: Pet = Body()):
        return pet

    @app.post("/pet/annotated")
    async def create_pet_annotated(pet: Annotated[Pet, Body()]):
        return pet

    client = TestClient(app)
    return client