diff --git a/pyproject.toml b/pyproject.toml
index a6ccbc4d6..e2e962719 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -91,7 +91,7 @@ addopts = """
     """
 # https://iscinumpy.gitlab.io/post/bound-version-constraints/#watch-for-warnings
 # https://github.com/DiamondLightSource/FastCS/issues/230
-# filterwarnings = "error"
+filterwarnings = "error"
 # Doctest python code in docs, python code in src docstrings, test functions in tests
 testpaths = "docs src tests"
 timeout = 1
diff --git a/tests/conftest.py b/tests/conftest.py
index f6770d5e9..21373247e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,3 +1,4 @@
+import asyncio
 import io
 import multiprocessing
 import os
@@ -236,3 +237,11 @@ def test_controller(tango_system, register_device):
 
     process.send_signal(signal.SIGINT)
     process.wait(timeout)
+
+
+@pytest.fixture
+def event_loop():
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.run_until_complete(loop.shutdown_asyncgens())
+    loop.close()
diff --git a/tests/test_launch.py b/tests/test_launch.py
index 36c505280..883fcdb9c 100644
--- a/tests/test_launch.py
+++ b/tests/test_launch.py
@@ -154,6 +154,14 @@ def test_error_if_identical_context_in_transports(mocker: MockerFixture, data):
         new_callable=mocker.PropertyMock,
         return_value={"controller": "test"},
     )
+    mocker.patch(
+        "fastcs.transport.epics.pva.transport.EpicsPVATransport.serve",
+        new_callable=mocker.PropertyMock,
+    )
+    mocker.patch(
+        "fastcs.transport.epics.ca.transport.EpicsCATransport.serve",
+        new_callable=mocker.PropertyMock,
+    )
     app = _launch(IsHinted)
     result = runner.invoke(app, ["run", str(data / "config.yaml")])
     assert isinstance(result.exception, RuntimeError)
diff --git a/tests/transport/tango/test_dsr.py b/tests/transport/tango/test_dsr.py
index 4883601f9..449732853 100644
--- a/tests/transport/tango/test_dsr.py
+++ b/tests/transport/tango/test_dsr.py
@@ -50,9 +50,7 @@ def create_test_context(tango_controller_api: AssertableControllerAPI):
     tango_transport = TangoTransport()
     tango_transport.connect(
         tango_controller_api,
-        # This is passed to enable instantiating the transport, but tests must avoid
-        # using via patching of functions. It will raise NotImplementedError if used.
-        asyncio.AbstractEventLoop(),
+        asyncio.get_event_loop(),
     )
     device = tango_transport._dsr._device
     # https://tango-controls.readthedocs.io/projects/pytango/en/v9.5.1/testing/test_context.html