diff --git a/aiohttp/pytest_plugin.py b/aiohttp/pytest_plugin.py
index 128dc46081d..029d8281dd3 100644
--- a/aiohttp/pytest_plugin.py
+++ b/aiohttp/pytest_plugin.py
@@ -208,6 +208,10 @@ def pytest_pyfunc_call(pyfuncitem):  # type: ignore[no-untyped-def]
     """Run coroutines in an event loop instead of a normal function call."""
     fast = pyfuncitem.config.getoption("--aiohttp-fast")
     if inspect.iscoroutinefunction(pyfuncitem.function):
+        warnings.warn(
+            "aiohttp.pytest_plugin will be removed in v4. Please install pytest-aiohttp.",
+            DeprecationWarning,
+        )
         existing_loop = pyfuncitem.funcargs.get(
             "proactor_loop"
         ) or pyfuncitem.funcargs.get("loop", None)
diff --git a/setup.cfg b/setup.cfg
index 83b33d01532..bec306f4f51 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -147,6 +147,7 @@ addopts =
 
     # run tests that are not marked with dev_mode
     -m "not dev_mode"
+asyncio_mode = auto
 filterwarnings =
     error
     ignore:module 'ssl' has no attribute 'OP_NO_COMPRESSION'. The Python interpreter is compiled against OpenSSL < 1.0.0. Ref. https.//docs.python.org/3/library/ssl.html#ssl.OP_NO_COMPRESSION:UserWarning