^{Originally posted by chris48s September 13, 2023}
Hello. I'm not really sure if this is an issue with starlette or httpx. It kind of sits at the intersection between the two. Here''s a minimal example application:

app.py:

from starlette.applications import Starlette
from starlette.responses import Response
from starlette.routing import Route

async def index(request):
    foo = request.query_params.get("foo")
    return Response(foo, status_code=200, media_type="text/html")

routes = [Route("/", endpoint=index)]

app = Starlette(debug=True, routes=routes)

..and here's a unit test (pytest):

test.py:

from starlette.testclient import TestClient

from app import app

def test_foo():
    client = TestClient(app)
    response = client.get("/?foo=%3A/")
    assert ":/" == response.text

If I run that test with

starlette==0.31.1
httpx==0.24.1

installed, the test passes.

Install

starlette==0.31.1
httpx==0.25.0

and run it again. The test now fails. The output is %3A/ not :/

Note that the actual application behaviour is unchanged. i.e: when invoked independently of TestClient (I'm serving with uvicorn app:app), the response is still :/ in either case.

This seems like it could be related to encode/httpx#2844 but I decided to open a discussion specifically about the impact on starlette TestClient