diff --git a/tests/conftest.py b/tests/conftest.py
index 4016ff0..e38e5e5 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1 +1,29 @@
-# Env var setup that must run before app.config is imported.
+from collections.abc import AsyncIterator
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.config import Settings
+from app.main import create_app
+from app.models import CurrentStatus, MonitorState, utc_now
+
+
+class FakeChecker:
+    async def check(self, monitor_id: str, target_url: str) -> CurrentStatus:
+        return CurrentStatus(
+            state=MonitorState.UP,
+            checked_at=utc_now(),
+            latency_ms=3.5,
+            http_status=204,
+        )
+
+
+@pytest.fixture
+def anyio_backend() -> str:
+    return "asyncio"
+
+
+@pytest.fixture
+def client() -> AsyncIterator[TestClient]:
+    with TestClient(create_app(Settings(), checker=FakeChecker())) as test_client:  # type: ignore[arg-type]
+        yield test_client