From ed049da34f663de4c1b4d9cc0654f958923eaf13 Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Wed, 23 Sep 2020 16:24:40 -0400
Subject: [PATCH] Add a helper that can render a Page or a Resource

---
 src/allmydata/test/common_web.py | 60 ++++++++++++++++++++++++++++++--
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/src/allmydata/test/common_web.py b/src/allmydata/test/common_web.py
index 1c9312689..d11e39383 100644
--- a/src/allmydata/test/common_web.py
+++ b/src/allmydata/test/common_web.py
@@ -1,9 +1,33 @@
 
 import treq
-from twisted.internet import defer
+from twisted.internet.defer import (
+    maybeDeferred,
+    inlineCallbacks,
+    returnValue,
+    succeed,
+)
 from twisted.web.error import Error
+from twisted.web.resource import (
+    IResource as ITwistedResource,
+)
+from twisted.web.test.requesthelper import (
+    DummyRequest,
+)
 
-@defer.inlineCallbacks
+from nevow.context import WebContext
+from nevow.testutil import FakeRequest
+from nevow.appserver import (
+    processingFailed,
+    DefaultExceptionHandler,
+)
+from nevow.inevow import (
+    ICanHandleException,
+    IRequest,
+    IResource as INevowResource,
+    IData,
+)
+
+@inlineCallbacks
 def do_http(method, url, **kwargs):
     response = yield treq.request(method, url, persistent=False, **kwargs)
     body = yield treq.content(response)
@@ -11,4 +35,34 @@ def do_http(method, url, **kwargs):
     # https://github.com/twisted/treq/pull/159 has landed
     if 400 <= response.code < 600:
         raise Error(response.code, response=body)
-    defer.returnValue(body)
+    returnValue(body)
+
+
+def render(resource, **query_args):
+    """
+    Render (in the manner of the Nevow appserver) a Nevow ``Page`` or a
+    Twisted ``Resource`` against a request with the given query arguments .
+
+    :param resource: The page or resource to render.
+
+    :param query_args: The query arguments to put into the request being
+        rendered.  A mapping from ``bytes`` to ``list`` of ``bytes``.
+
+    :return Deferred: A Deferred that fires with the rendered response body as
+        ``bytes``.
+    """
+    ctx = WebContext(tag=resource)
+    req = FakeRequest(args=query_args)
+    ctx.remember(DefaultExceptionHandler(), ICanHandleException)
+    ctx.remember(req, IRequest)
+    ctx.remember(None, IData)
+
+    def maybe_concat(res):
+        if isinstance(res, bytes):
+            return req.v + res
+        return req.v
+
+    resource = INevowResource(resource)
+    d = maybeDeferred(resource.renderHTTP, ctx)
+    d.addCallback(maybe_concat)
+    return d