TestClient accepts backend and backend_options as arguments

docs/testclient.md

@@ -33,18 +33,25 @@ case you should use `client = TestClient(app, raise_server_exceptions=False)`.
 
 ### Selecting the Async backend
 
-`TestClient.async_backend` is a dictionary which allows you to set the options
-for the backend used to run tests.  These options are passed to
-`anyio.start_blocking_portal()`. See the [anyio documentation](https://anyio.readthedocs.io/en/stable/basics.html#backend-options)
-for more information about backend options.  By default, `asyncio` is used.
+`TestClient` takes arguments `backend` (a string) and `backend_options` (a dictionary).
+These options are passed to `anyio.start_blocking_portal()`. See the [anyio documentation](https://anyio.readthedocs.io/en/stable/basics.html#backend-options)
+for more information about the accepted backend options.
+By default, `asyncio` is used with default options.
 
-To run `Trio`, set `async_backend["backend"] = "trio"`, for example:
+To run `Trio`, pass `backend="trio"`. For example:
 
 ```python
 def test_app()
-    client = TestClient(app)
-    client.async_backend["backend"] = "trio"
-    ...
+    with TestClient(app, backend="trio") as client:
+       ...
+```
+
+To run `asyncio` with `uvloop`, pass `backend_options={"use_uvloop": True}`.  For example:
+
+```python
+def test_app()
+    with TestClient(app, backend_options={"use_uvloop": True}) as client:
+       ...
 ```
 
 ### Testing WebSocket sessions

starlette/testclient.py

@@ -381,13 +381,11 @@ def receive_json(self, mode: str = "text") -> typing.Any:
 
 class TestClient(requests.Session):
     __test__ = False  # For pytest to not discover this up.
-
-    #: These options are passed to `anyio.start_blocking_portal()`
+    #: These are the default options for the constructor arguments
     async_backend: typing.Dict[str, typing.Any] = {
         "backend": "asyncio",
         "backend_options": {},
     }
-
     task: "Future[None]"
 
     def __init__(
@@ -396,8 +394,14 @@ def __init__(
         base_url: str = "http://testserver",
         raise_server_exceptions: bool = True,
         root_path: str = "",
+        backend: typing.Optional[str] = None,
+        backend_options: typing.Optional[typing.Dict[str, typing.Any]] = None,
     ) -> None:
         super().__init__()
+        self.async_backend = {
+            "backend": backend or self.async_backend["backend"],
+            "backend_options": backend_options or self.async_backend["backend_options"],
+        }
         if _is_asgi3(app):
             app = typing.cast(ASGI3App, app)
             asgi_app = app

tests/test_testclient.py

@@ -132,3 +132,22 @@ async def asgi(receive, send):
     with client.websocket_connect("/") as websocket:
         data = websocket.receive_json()
         assert data == {"message": "test"}
+
+
+def test_backend_name(request):
+    """
+    Test that the tests are defaulting to the correct backend and that a new
+    instance of TestClient can be created using different backend options.
+    """
+    # client created using monkeypatched async_backend
+    client1 = TestClient(mock_service)
+    if "trio" in request.keywords:
+        client2 = TestClient(mock_service, backend="asyncio")
+        assert client1.async_backend["backend"] == "trio"
+        assert client2.async_backend["backend"] == "asyncio"
+    elif "asyncio" in request.keywords:
+        client2 = TestClient(mock_service, backend="trio")
+        assert client1.async_backend["backend"] == "asyncio"
+        assert client2.async_backend["backend"] == "trio"
+    else:
+        pytest.fail("Unknown backend")  # pragma: nocover