Disconnect event not received when using TestClient

[AGhost-7]

Checklist

• The bug is reproducible against the latest release and/or master.
• There are no similar issues or pull requests to fix it yet.

Describe the bug

When using the TestClient provided by the starlette framework, http.disconnect are not received. This is a problem if trying to test streaming.

To reproduce

Implement simple app:

async def app(scope, receive, send):
    await send({
        'type': 'http.response.start',
        'status': 200,
    })
    while True:
        message = await receive()
        print('message', message)
        if message['type'] == 'http.disconnect':
            break

Write test using provided TestClient, which closes the connection during "processing":

from bug import app
from starlette.testclient import TestClient

client = TestClient(app)

def test_client():
    response = client.post('/', stream=True)
    print('response.status', response.status)
    response.close()

Expected behavior

The server behaviour should be the same if using TestClient or Uvicorn. If I run the application provided above with Uvicorn:

uvicorn bug:app

And write a test using the normal requests as follows:

import requests

def test_server():
    response = requests.post('http://localhost:8000/', stream=True)
    print('response.status', response.status)
    response.close()

The http.disconnect event is received. This should be the same for the TestClient

Actual behavior

No http.disconnect event is received by the app when using TestClient.

Debugging material

Environment

• OS: Linux
• Python version: 3.8.10
• Starlette version: 0.16.0

Additional context

[Kludex]

We should take care of this for #652 , I guess.

[Kludex]

I think this will always be a limitation of the TestClient. I think we should add a test case, and maybe add a few lines on the documentation on how to test this.

[Kludex]

A way to test an ASGI application with http.disconnect without the TestClient: #1727