Simulate multipart/form-data file upload with Falcon's Testing module

This simple Falcon API will take a HTTP POST with enctype=multipart/form-data and a file upload in the file parameter, returning the file's content to the caller:

# simple_api.py
import cgi
import falcon
import json

class MultipartFileUpload(object):
    def on_post(self, req, resp):
        upload = cgi.FieldStorage(fp=req.stream, environ=req.env)
        data = upload['file'].file.read().decode('utf-8')
        resp.body = json.dumps(dict(data=data))

app = falcon.API()
app.add_route('/', MultipartFileUpload())

To try this out, create a textfile with some content and send to the API via curl -F "file=@sample.txt" localhost:8000.

I would like to test this API now with Falcon's testing utilities, simulating such a file upload. The simulate_request method has a file_wrapper parameter which might be useful but from the documentation I do not understand how it is supposed to be used or whether this is possible at all.

As a workaround, I currently use webtest where this is supported, another possibility would be werkzeug. Anyway, I'm happy to drop dependencies if this should be possible with Falcon itself.