correct variable name in testing docs (#913)

* correct variable name in testing docs

* more corrections and make TestClient.app public

aiohttp/test_utils.py

@@ -326,16 +326,16 @@ class TestClient:
 
     :type app: aiohttp.web.Application
 
-    :param protocol: the aiohttp.web application passed to create_test_server
+    :param protocol: http or https
 
-    :type app: aiohttp.web.Application
+    :type protocol: str
 
     TestClient can also be used as a contextmanager, returning
     the instance of itself instantiated.
     """
 
     def __init__(self, app, protocol="http"):
-        self._app = app
+        self.app = app
         self._loop = loop = app.loop
         self.port = unused_port()
         self._handler = handler = app.make_handler()
@@ -418,7 +418,7 @@ def close(self):
             loop = self._loop
             loop.run_until_complete(self._session.close())
             loop.run_until_complete(self._handler.finish_connections())
-            loop.run_until_complete(self._app.finish())
+            loop.run_until_complete(self.app.finish())
             self._server.close()
             loop.run_until_complete(self._server.wait_closed())
             self._closed = True

docs/testing.rst

@@ -73,21 +73,21 @@ Pytest example
 A pytest example could look like::
 
     # assuming you are using pytest-asyncio
-    from asyncio.test_utils import TestClient, loop_context
+    from aiohttp.test_utils import TestClient, loop_context
 
     @pytest.yield_fixture
     def loop():
         with loop_context() as loop:
             yield loop
 
     @pytest.fixture
-    def app(test_loop):
-        return create_app(event_loop)
+    def app(loop):
+        return create_app(loop)
 
 
     @pytest.yield_fixture
     def test_client(app):
-        server = TestClient(app)
+        client = TestClient(app)
         yield client
         client.close()