It is designed to have functions that receive two parameters, one "request" and one "response". Then you "read" parts from the request, and "write" parts to the response. Because of this design, it is not possible to declare request parameters and bodies with standard Python type hints as function parameters.

    ```

    Note that for OAuth2 the scope `items:read` is a single scope in an opaque string.
    You could have custom internal logic to separate it by colon caracters (`:`) or
    similar, and get the two parts `items` and `read`. Many applications do that to
    group and organize permissions, you could do it as well in your application, just
    know that that it is application specific, it's not part of the specification.
    """

* Do not change the paths in links to images, code files, Markdown documents.

* However, when a Markdown document is translated, the `#hash-parts` in links to its headings may change. Update these links if possible.
    * Search for such links in the translated document using the regex `#[^# ]`.

{!../../../docs_src/app_testing/test_main.py!}
```

...and have the code for the tests just like before.

## Testing: extended example

Now let's extend this example and add more details to see how to test different parts.

### Extended **FastAPI** app file

Let's continue with the same file structure as before:

```
.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py
```

# Reference - Code API

Here's the reference or code API, the classes, functions, parameters, attributes, and
all the FastAPI parts you can use in your applications.

If you want to **learn FastAPI** you are much better off reading the

# Using the Request Directly

Up to now, you have been declaring the parts of the request that you need with their types.

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

    * The contents are **encrypted**, even though they are being sent with the **HTTP protocol**.

By creating a function that is only dedicated to getting your user from a `username` (or any other parameter) independent of your *path operation function*, you can more easily re-use it in multiple parts and also add <abbr title="Automated test, written in code, that checks if another piece of code is working correctly.">unit tests</abbr> for it:

```Python hl_lines="36-42"
{!../../../docs_src/nosql_databases/tutorial001.py!}

The sequence of execution before FastAPI 0.106.0 was like this diagram:

Time flows from top to bottom. And each column is one of the parts interacting or executing code.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation

    - 💾 [PostgreSQL](https://www.postgresql.org) as the SQL database.
- 🚀 [React](https://react.dev) for the frontend.
    - 💃 Using TypeScript, hooks, Vite, and other parts of a modern frontend stack.
    - 🎨 [Chakra UI](https://chakra-ui.com) for the frontend components.
    - 🤖 An automatically generated frontend client.
    - 🦇 Dark mode support.