And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

As **FastAPI** is based on Starlette and implements the <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr> specification, you can use any ASGI middleware.

Your normal dependency `get_db()` would return a database session.

In the test, you could use a dependency override to return your *custom* database session instead of the one that would be used normally.

In this example we'll create a temporary database only for the tests.

## File structure

We create a new file at `sql_app/tests/test_sql_app.py`.

So the new file structure looks like:

``` hl_lines="9-11"
.
└── sql_app

* Memory
* Previous steps before starting

We'll see how they would affect **deployments**.

In the end, the ultimate objective is to be able to **serve your API clients** in a way that is **secure**, to **avoid disruptions**, and to use the **compute resources** (for example remote servers/virtual machines) as efficiently as possible. 🚀

    ```

`Field` works the same way as `Query`, `Path` and `Body`, it has all the same parameters, etc.

!!! note "Technical Details"
    Actually, `Query`, `Path` and others you'll see next create objects of subclasses of a common `Param` class, which is itself a subclass of Pydantic's `FieldInfo` class.

    And Pydantic's `Field` returns an instance of `FieldInfo` as well.

@app.webhooks.post("new-subscription")
def new_subscription(
    body: Subscription, token: Annotated[str, Security(bearer_scheme)]
):
    """
    When a new user subscribes to your service we'll send you a POST request with this
    data to the URL that you register for the event `new-subscription` in the dashboard.
    """


client = TestClient(app)


def test_dummy_webhook():
    # Just for coverage

* Security - HTTPS
* Running on startup
* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

        },
        "webhooks": {
            "new-subscription": {
                "post": {
                    "summary": "New Subscription",
                    "description": "When a new user subscribes to your service we'll send you a POST request with this\ndata to the URL that you register for the event `new-subscription` in the dashboard.",
                    "operationId": "new_subscriptionnew_subscription_post",
                    "requestBody": {

But I'll show you how to improve that next. 🤓

## Custom Operation IDs and Better Method Names

You can **modify** the way these operation IDs are **generated** to make them simpler and have **simpler method names** in the clients.

Let's use the tools provided by **FastAPI** to handle security.

## How it looks

Let's first just use the code and see how it works, and then we'll come back to understand what's happening.

## Create `main.py`

Copy the example in a file `main.py`:

=== "Python 3.9+"

    ```Python
    {!> ../../../docs_src/security/tutorial001_an_py39.py!}
    ```

In this case, it would use the certificate for `someapp.example.com`.

<img src="/img/deployment/https/https03.svg">

The client already **trusts** the entity that generated that TLS certificate (in this case Let's Encrypt, but we'll see about that later), so it can **verify** that the certificate is valid.