add latency-based test

tests/test_group.py

@@ -3,6 +3,7 @@
 import contextlib
 import operator
 import pickle
+import time
 import warnings
 from typing import TYPE_CHECKING, Any, Literal
 
@@ -22,6 +23,7 @@
 from zarr.errors import ContainsArrayError, ContainsGroupError
 from zarr.storage import LocalStore, MemoryStore, StorePath, ZipStore
 from zarr.storage.common import make_store_path
+from zarr.testing.store import LatencyStore
 
 from .conftest import parse_store
 
@@ -1484,3 +1486,23 @@ def test_delitem_removes_children(store: Store, zarr_format: ZarrFormat) -> None
     del g1["0"]
     with pytest.raises(KeyError):
         g1["0/0"]
+
+
+@pytest.mark.parametrize('store', ['memory'], indirect=True)
+def test_group_members_performance(store: MemoryStore) -> None:
+    """
+    Test that the performance of Group.members is robust to asynchronous latency
+    """
+    get_latency = 0.1
+    latency_store = LatencyStore(store, get_latency=get_latency)
+
+    group = zarr.group(store=latency_store)
+    num_groups = 100
+    # Create some groups
+    for i in range(num_groups):
+        group.create_group(f"group{i}")
+
+    start= time.time()
+    members = group.members()
+    elapsed = start = time.time()
+    assert elapsed < 2 * get_latency