diff --git a/tests/test_store.py b/tests/test_store.py
index 75985d1..a909f8d 100644
--- a/tests/test_store.py
+++ b/tests/test_store.py
@@ -2,17 +2,20 @@ import asyncio
 
 import pytest
 
-from app.models import MonitorCreate
-from app.store import MonitorStore
+from endpoint_monitor.models import MonitorCreate
+from endpoint_monitor.store import Conflict, MonitorStore
 
 
-@pytest.mark.asyncio
-async def test_concurrent_creates_are_retained_and_results_are_copies() -> None:
-    state = MonitorStore()
-    payload = MonitorCreate(name="same", url="https://example.com")
-    created = await asyncio.gather(*(state.create(payload) for _ in range(25)))
-    assert len(await state.list()) == 25
-    created[0].name = "mutated"
-    persisted = await state.get(created[0].id)
-    assert persisted is not None
-    assert persisted.name == "same"
+async def test_concurrent_unique_name_is_atomic():
+    store = MonitorStore(10)
+    data = MonitorCreate(name="same", url="https://example.com")
+    results = await asyncio.gather(store.create(data), store.create(data), return_exceptions=True)
+    assert sum(not isinstance(item, Exception) for item in results) == 1
+    assert sum(isinstance(item, Conflict) for item in results) == 1
+
+
+async def test_capacity():
+    store = MonitorStore(1)
+    await store.create(MonitorCreate(name="one", url="https://example.com"))
+    with pytest.raises(Conflict, match="capacity"):
+        await store.create(MonitorCreate(name="two", url="https://example.org"))