assert response.status_code == 200, response.text
    assert response.json() == {"message": "No file sent"}


@needs_py39
def test_post_uploadfile_no_body(client: TestClient):
    response = client.post("/uploadfile/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No upload file sent"}


@needs_py39
def test_post_file(tmp_path: Path, client: TestClient):

    Note over client,operation: Response is already sent, can't change it anymore
    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> tasks: Handle exceptions in the background task code
    end
```

!!! info

### The callback path expression

The callback *path* can have an <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.1.0.md#key-expression" class="external-link" target="_blank">OpenAPI 3 expression</a> that can contain parts of the original request sent to *your API*.

In this case, it's the `str`:

```Python

        background_tasks.add_task(write_log, message)
    return q


@app.post("/send-notification/{email}")
async def send_notification(
    email: str, background_tasks: BackgroundTasks, q: Annotated[str, Depends(get_query)]
):
    message = f"message to {email}\n"
    background_tasks.add_task(write_log, message)

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

    This is because uploaded files are sent as "form data".

## Import `File`

Import `File` and `UploadFile` from `fastapi`:

=== "Python 3.9+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/request_files/tutorial001_an_py39.py!}
    ```

    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No file sent"}


@needs_py310
def test_post_uploadfile_no_body(client: TestClient):
    response = client.post("/uploadfile/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No upload file sent"}


@needs_py310
def test_post_file(tmp_path: Path, client: TestClient):

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:

    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No file sent"}


@needs_py310
def test_post_uploadfile_no_body(client: TestClient):
    response = client.post("/uploadfile/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No upload file sent"}


@needs_py310
def test_post_file(tmp_path: Path, client: TestClient):

    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No file sent"}


def test_post_uploadfile_no_body():
    response = client.post("/uploadfile/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "No upload file sent"}


def test_post_file(tmp_path):
    path = tmp_path / "test.txt"
    path.write_bytes(b"<file content>")

from dirty_equals import IsDict
from fastapi.testclient import TestClient

from docs_src.schema_extra_example.tutorial004 import app

client = TestClient(app)


# Test required and embedded body parameters with no bodies sent
def test_post_body_example():
    response = client.put(
        "/items/5",
        json={
            "name": "Foo",
            "description": "A very nice Item",
            "price": 35.4,