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

## pytest.mark.anyio

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

!!! tip
    Notice that here as we are using standard `open()` that doesn't support `async` and `await`, we declare the path operation with normal `def`.

### `FileResponse`

Asynchronously streams a file as the response.

Takes a different set of arguments to instantiate than the other response types:

* `path` - The filepath to the file to stream.

):
    return value


@app.get("/asynchronous-method-dependency")
async def get_asynchronous_method_dependency(
    value: str = Depends(methods_dependency.asynchronous),
):
    return value


@app.get("/asynchronous-method-gen-dependency")
async def get_asynchronous_method_gen_dependency(
    value: str = Depends(methods_dependency.asynchronous_gen),
):
    return value

* **Asynchronous Code**
* **`async` and `await`**
* **Coroutines**

## Asynchronous Code

Asynchronous code just means that the language 💬 has a way to tell the computer / program 🤖 that at some point in the code, it 🤖 will have to wait for *something else* to finish somewhere else. Let's say that *something else* is called "slow-file" 📝.

So, during that time, the computer can go and do some other work, while "slow-file" 📝 finishes.

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.

A middleware doesn't have to be made for FastAPI or Starlette to work, as long as it follows the ASGI spec.

!!! 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

### <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a>

Starlette is a lightweight <abbr title="The new standard for building asynchronous Python web applications">ASGI</abbr> framework/toolkit, which is ideal for building high-performance asyncio services.

It is very simple and intuitive. It's designed to be easily extensible, and have modular components.

## ASGI Servers

Let's go a little deeper into the details.

FastAPI uses a standard for building Python web frameworks and servers called <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr>. FastAPI is an ASGI web framework.

    **FastAPI** ⤴️ ✊ 👈 🎻 🔗 💽 & 🚮 ⚫️ 🗄, ↖️ ⚪️➡️ 🌐 🎏 👜 ⚫️ 🔨.

### <a href="https://www.starlette.io/" class="external-link" target="_blank">💃</a>

💃 💿 <abbr title="The new standard for building asynchronous Python web">🔫</abbr> 🛠️/🧰, ❔ 💯 🏗 ↕-🎭 ✳ 🐕‍🦺.

⚫️ 📶 🙅 &amp; 🏋️. ⚫️ 🔧 💪 🏧, &amp; ✔️ 🔧 🦲.

⚫️ ✔️:

* 🤙 🎆 🎭.
*  *️⃣ 🐕‍🦺.
* -🛠️ 🖥 📋.
* 🕴 &amp; 🤫 🎉.
* 💯 👩‍💻 🏗 🔛 🇸🇲.

# 並行処理と async / await

*path operation 関数*のための `async def` に関する詳細と非同期 (asynchronous) コード、並行処理 (Concurrency)、そして、並列処理 (Parallelism) の背景について。

## 急いでいますか？

<abbr title="too long; didn't read (長すぎて読めない人のための要約という意味のスラング)"><strong>TL;DR:</strong></abbr>

次のような、`await` を使用して呼び出すべきサードパーティライブラリを使用している場合:

```Python
results = await some_library()
```

以下の様に `async def` を使用して*path operation 関数*を宣言します。

```Python hl_lines="2"
@app.get('/')