# Sub Applications - Mounts { #sub-applications-mounts }

If you need to have two independent FastAPI applications, with their own independent OpenAPI and their own docs UIs, you can have a main app and "mount" one (or more) sub-application(s).

## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

from fastapi import Depends, FastAPI, Security
from fastapi.security import APIKeyHeader
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

api_key = APIKeyHeader(name="key")


class User(BaseModel):
    username: str


def get_current_user(oauth_header: str = Security(api_key)):
    user = User(username=oauth_header)
    return user


@app.get("/users/me")

from fastapi import Depends, FastAPI, Security
from fastapi.security import APIKeyHeader
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

api_key = APIKeyHeader(name="key", description="An API Key Header")


class User(BaseModel):
    username: str


def get_current_user(oauth_header: str = Security(api_key)):
    user = User(username=oauth_header)
    return user

You could also use `from starlette.testclient import TestClient`.

**FastAPI** provides the same `starlette.testclient` as `fastapi.testclient` just as a convenience for you, the developer. But it comes directly from Starlette.

///

/// tip

## Es testen { #check-it }

Jetzt wird jeder <abbr title="Request – Anfrage: Daten, die der Client zum Server sendet">Request</abbr> unter dem Pfad `/v1/` von der Flask-Anwendung verarbeitet.

Und der Rest wird von **FastAPI** gehandhabt.

# Запити з формами та файлами

У FastAPI Ви можете одночасно отримувати файли та поля форми, використовуючи `File` і `Form`.

/// info | Інформація

Щоб отримувати завантажені файли та/або дані форми, спочатку встановіть <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">python-multipart</a>.

from fastapi.testclient import TestClient

from docs_src.handling_errors.tutorial006_py39 import app

client = TestClient(app)


def test_get_validation_error():
    response = client.get("/items/foo")
    assert response.status_code == 422, response.text
    assert response.json() == {
        "detail": [
            {
                "type": "int_parsing",
                "loc": ["path", "item_id"],

    return mod


def test_say_hi(module: ModuleType):
    with patch("builtins.print") as mock_print:
        module.say_hi("FastAPI")
        module.say_hi()

    assert mock_print.call_count == 2
    call_args = [arg.args for arg in mock_print.call_args_list]
    assert call_args == [
        ("Hey FastAPI!",),
        ("Hello World",),

    return mod


def test_say_hi(module: ModuleType):
    with patch("builtins.print") as mock_print:
        module.say_hi("FastAPI")

    mock_print.assert_called_once_with("Hey FastAPI!")

    with pytest.raises(
        TypeError,
        match=re.escape("say_hi() missing 1 required positional argument: 'name'"),
    ):

# Öğren

**FastAPI** öğrenmek için giriş bölümleri ve öğreticiler burada yer alıyor.