!!! 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

    First install <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>.

    E.g. `pip install python-multipart`.

    This is because **OAuth2** uses "form data" for sending the `username` and `password`.

Run the example with:

<div class="termy">

```console
$ uvicorn main:app --reload

# OpenAPI Webhooks

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps

## Reporting a Vulnerability

If you think you found a vulnerability, and even if you are not sure about it, please report it right away by sending an email to: ******@****.***. Please try to be as explicit as possible, describing all the steps and example code to reproduce the security issue.

The process that happens when your API app calls the *external API* is named a "callback". Because the software that the external developer wrote sends a request to your API and then your API *calls back*, sending a request to an *external API* (that was probably created by the same developer).

Being able to use asynchronous functions in your tests could be useful, for example, when you're querying your database asynchronously. Imagine you want to test sending requests to your FastAPI application and then verify that your backend successfully wrote the correct data in the database, while using an async database library.

Let's look at how we can make that work.

## pytest.mark.anyio

    So, you will have to make sure your data is of the correct type. E.g. it is compatible with JSON, if you are returning a `JSONResponse`.

    And also that you are not sending any data that should have been filtered by a `response_model`.

### More info

!!! note "Technical Details"
    You could also use `from starlette.responses import Response` or `from starlette.responses import JSONResponse`.

This includes, for example:

* Email notifications sent after performing an action:
    * As connecting to an email server and sending an email tends to be "slow" (several seconds), you can return the response right away and send the email notification in the background.
* Processing data:

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="9"
    {!> ../../../docs_src/header_params/tutorial003.py!}
    ```

If you communicate with that *path operation* sending two HTTP headers like:

```
X-Token: foo
X-Token: bar
```

The response would be like:

```JSON
{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

You could use it while developing your app to log the body and debug it, return it to the user, etc.

```Python hl_lines="14"
{!../../../docs_src/handling_errors/tutorial005.py!}
```

Now try sending an invalid item like:

```JSON
{
  "title": "towel",
  "size": "XL"
}
```

You will receive a response telling you that the data is invalid containing the received body: