diff --git a/tests/test_atomic.py b/tests/test_atomic.py
new file mode 100644
index 0000000..a29b45d
--- /dev/null
+++ b/tests/test_atomic.py
@@ -0,0 +1,31 @@
+import asyncio
+
+import pytest
+
+from app.models import CurrentStatus, HealthState, MonitorCreate, MonitorUpdate, utc_now
+from app.store import MonitorStore
+
+
+@pytest.mark.asyncio
+async def test_status_compare_and_set_rejects_stale_revision() -> None:
+    store = MonitorStore()
+    item = await store.create(MonitorCreate(name="old", url="https://example.com/a"))
+    result = CurrentStatus(state=HealthState.up, checked_at=utc_now(), latency_ms=1, http_status=200)
+
+    await store.update(item.id, MonitorUpdate(name="new", url="https://example.com/b"))
+    assert await store.set_status_if_current(item.id, item.revision, result) is False
+    current = await store.get(item.id)
+    assert current is not None and current.current_status is None
+
+
+@pytest.mark.asyncio
+async def test_concurrent_writes_remain_consistent() -> None:
+    store = MonitorStore()
+    item = await store.create(MonitorCreate(name="start", url="https://example.com"))
+    await asyncio.gather(*[
+        store.update(item.id, MonitorUpdate(name=f"name-{index}", url="https://example.com"))
+        for index in range(20)
+    ])
+    current = await store.get(item.id)
+    assert current is not None
+    assert current.revision == 21