diff --git a/tests/test_store.py b/tests/test_store.py
new file mode 100644
index 0000000..5412f02
--- /dev/null
+++ b/tests/test_store.py
@@ -0,0 +1,39 @@
+import asyncio
+
+import pytest
+
+from app.models import CurrentStatus, MonitorCreate, MonitorUpdate, State
+from app.store import MonitorStore
+
+
+@pytest.mark.asyncio
+async def test_concurrent_creates_are_not_lost() -> None:
+    store = MonitorStore()
+    await asyncio.gather(*[
+        store.create(MonitorCreate(name=f"m-{number}", url=f"https://example.com/{number}"))
+        for number in range(100)
+    ])
+    assert len(await store.list()) == 100
+
+
+@pytest.mark.asyncio
+async def test_stale_check_cannot_overwrite_updated_monitor() -> None:
+    store = MonitorStore()
+    item = await store.create(MonitorCreate(name="old", url="https://example.com"))
+    snapshot = await store.snapshot(item.id)
+    assert snapshot is not None
+    _, revision = snapshot
+    await store.update(item.id, MonitorUpdate(name="new"))
+    recorded = await store.record_status(item.id, revision, CurrentStatus(state=State.UP))
+    assert recorded is None
+    current = await store.get(item.id)
+    assert current is not None and current.current_status.state == State.UNKNOWN
+
+
+@pytest.mark.asyncio
+async def test_defensive_copy_does_not_mutate_store() -> None:
+    store = MonitorStore()
+    item = await store.create(MonitorCreate(name="safe", url="https://example.com"))
+    item.name = "outside"
+    stored = await store.get(item.id)
+    assert stored is not None and stored.name == "safe"