From ed16b7df21174892095a0665c1e816a2a2ed306e Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Fri, 23 Nov 2018 11:11:16 +0000
Subject: [PATCH] Asyncio cleanups (#236)

---
 starlette/middleware/wsgi.py | 21 +++++++++++++--------
 starlette/testclient.py      |  6 +++++-
 tests/test_testclient.py     | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 9 deletions(-)
 create mode 100644 tests/test_testclient.py

diff --git a/starlette/middleware/wsgi.py b/starlette/middleware/wsgi.py
index b8006dac..eedb144b 100644
--- a/starlette/middleware/wsgi.py
+++ b/starlette/middleware/wsgi.py
@@ -81,14 +81,19 @@ class WSGIResponder:
             body += message.get("body", b"")
             more_body = message.get("more_body", False)
         environ = build_environ(self.scope, body)
-        wsgi = run_in_threadpool(self.wsgi, environ, self.start_response)
-        sender = self.loop.create_task(self.sender(send))
-        await asyncio.wait_for(wsgi, None)
-        self.send_queue.append(None)
-        self.send_event.set()
-        await asyncio.wait_for(sender, None)
-        if self.exc_info is not None:
-            raise self.exc_info[0].with_traceback(self.exc_info[1], self.exc_info[2])
+        try:
+            sender = self.loop.create_task(self.sender(send))
+            await run_in_threadpool(self.wsgi, environ, self.start_response)
+            self.send_queue.append(None)
+            self.send_event.set()
+            await asyncio.wait_for(sender, None)
+            if self.exc_info is not None:
+                raise self.exc_info[0].with_traceback(
+                    self.exc_info[1], self.exc_info[2]
+                )
+        finally:
+            if not sender.done():
+                sender.cancel()  # pragma: no cover
 
     async def sender(self, send: Send) -> None:
         while True:
diff --git a/starlette/testclient.py b/starlette/testclient.py
index ee575407..faac9839 100644
--- a/starlette/testclient.py
+++ b/starlette/testclient.py
@@ -181,7 +181,11 @@ class _ASGIAdapter(requests.adapters.HTTPAdapter):
         response_complete = False
         raw_kwargs = {"body": io.BytesIO()}  # type: typing.Dict[str, typing.Any]
 
-        loop = asyncio.get_event_loop()
+        try:
+            loop = asyncio.get_event_loop()
+        except RuntimeError:
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
 
         try:
             connection = self.app(scope)
diff --git a/tests/test_testclient.py b/tests/test_testclient.py
new file mode 100644
index 00000000..e6a81988
--- /dev/null
+++ b/tests/test_testclient.py
@@ -0,0 +1,32 @@
+from starlette.applications import Starlette
+from starlette.responses import JSONResponse
+from starlette.testclient import TestClient
+
+mock_service = Starlette()
+
+
+@mock_service.route("/")
+def mock_service_endpoint(request):
+    return JSONResponse({"mock": "example"})
+
+
+app = Starlette()
+
+
+@app.route("/")
+def homepage(request):
+    client = TestClient(mock_service)
+    response = client.get("/")
+    return JSONResponse(response.json())
+
+
+def test_use_testclient_in_endpoint():
+    """
+    We should be able to use the test client within applications.
+
+    This is useful if we need to mock out other services,
+    during tests or in development.
+    """
+    client = TestClient(app)
+    response = client.get("/")
+    assert response.json() == {"mock": "example"}