Test for aiohttp failure when backoff is used

tests/python35/test_aiohttp.py

@@ -0,0 +1,37 @@
+import pytest
+
+import backoff
+
+aiohttp = pytest.importorskip("aiohttp")
+aiohttp.web = pytest.importorskip("aiohttp.web")
+aiohttp.web_exceptions = pytest.importorskip("aiohttp.web_exceptions")
+
+
+async def test_backoff_on_all_session_requests(aiohttp_client):
+    call_count = 0
+
+    async def handler(request):
+        nonlocal call_count
+        call_count += 1
+        raise aiohttp.web_exceptions.HTTPUnauthorized
+
+    app = aiohttp.web.Application()
+    app.router.add_get('/', handler)
+    client = await aiohttp_client(
+        app,
+        connector=aiohttp.TCPConnector(limit=1),
+        raise_for_status=True,
+    )
+
+    # retry every session request
+    client._session._request = backoff.on_exception(
+        wait_gen=backoff.expo,
+        exception=aiohttp.client_exceptions.ClientResponseError,
+        max_tries=2,
+    )(client._session._request)
+
+    with pytest.raises(aiohttp.client_exceptions.ClientResponseError) as exc:
+        await client.get('/')
+
+    assert exc.value.code == 401
+    assert call_count == 2