```Python hl_lines="2  12  15-18"
{!../../../docs_src/app_testing/tutorial001.py!}
```

!!! tip
    Notice that the testing functions are normal `def`, not `async def`.

    And the calls to the client are also normal calls, not using `await`.

    This allows you to use `pytest` directly without complications.

!!! note "Technical Details"
    You could also use `from starlette.testclient import TestClient`.

Vorgang, der stattfindet, wenn Ihre API-Anwendung die *externe API* aufruft, wird als „Callback“ („Rückruf“) bezeichnet. Denn die Software, die der externe Entwickler geschrieben hat, sendet einen Request an Ihre API und dann *ruft Ihre API zurück* (*calls back*) und sendet einen Request an eine *externe API* (die wahrscheinlich vom selben Entwickler erstellt wurde).

In diesem Fall möchten Sie möglicherweise dokumentieren, wie diese externe API aussehen *sollte*. Welche *Pfadoperation* sie haben...

module = "fastapi.tests.*"
ignore_missing_imports = true
check_untyped_defs = true

[[tool.mypy.overrides]]
module = "docs_src.*"
disallow_incomplete_defs = false
disallow_untyped_defs = false
disallow_untyped_calls = false

[tool.pytest.ini_options]
addopts = [
  "--strict-config",
  "--strict-markers",
  "--ignore=docs_src",
]
xfail_strict = true
junit_family = "xunit2"
filterwarnings = [
    "error",

* ✏ Fix typos in Deployment Guide. PR [#3975](https://github.com/tiangolo/fastapi/pull/3975) by [@ghandic](https://github.com/ghandic).
* 📝 Update docs with pip install calls when using extras with brackets, use quotes for compatibility with Zsh. PR [#3131](https://github.com/tiangolo/fastapi/pull/3131) by [@tomwei7](https://github.com/tomwei7).

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).

## Other Asynchronous Function Calls

As the testing function is now asynchronous, you can now also call (and `await`) other `async` functions apart from sending requests to your FastAPI application in your tests, exactly as you would call them anywhere else in your code.

!!! tip

### Other utility functions

Any other utility function that you call directly can be created with normal `def` or `async def` and FastAPI won't affect the way you call it.

This is in contrast to the functions that FastAPI calls for you: *path operation functions* and dependencies.

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

    ```Python hl_lines="19"
    {!> ../../../docs_src/dependencies/tutorial002.py!}
    ```

**FastAPI** calls the `CommonQueryParams` class. This creates an "instance" of that class and the instance will be passed as the parameter `commons` to your function.

## Type annotation vs `Depends`

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

    ```Python hl_lines="1  10"
    {!> ../../../docs_src/settings/app03/main.py!}
    ```

Then for any subsequent calls of `get_settings()` in the dependencies for the next requests, instead of executing the internal code of `get_settings()` and creating a new `Settings` object, it will return the same object that was returned on the first call, again and again.

            by_alias: bool = True,
            exclude_unset: bool = False,
            exclude_defaults: bool = False,
            exclude_none: bool = False,
        ) -> Any:
            # What calls this code passes a value that already called
            # self._type_adapter.validate_python(value)
            return self._type_adapter.dump_python(
                value,
                mode=mode,