diff --git a/dkist/conftest.py b/dkist/conftest.py
index b6a78ae64..8f4d71c86 100644
--- a/dkist/conftest.py
+++ b/dkist/conftest.py
@@ -24,8 +24,9 @@
 
 @pytest.fixture
 def array():
-    shape = np.random.randint(10, 100, size=2)
-    x = np.ones(shape) + 10
+    shape = 2**np.random.randint(2, 7, size=2)
+    x = np.ones(np.prod(shape)) + 10
+    x = x.reshape(shape)
     return da.from_array(x, tuple(shape))
 
 
diff --git a/dkist/io/asdf/tests/test_dataset.py b/dkist/io/asdf/tests/test_dataset.py
index f321f03d0..43c6a7a10 100644
--- a/dkist/io/asdf/tests/test_dataset.py
+++ b/dkist/io/asdf/tests/test_dataset.py
@@ -1,5 +1,6 @@
 import sys
 from pathlib import Path
+from unittest.mock import call
 
 if sys.version_info < (3, 9):
     import importlib_resources
@@ -140,3 +141,35 @@ def test_read_all_schema_versions(eit_dataset_asdf_path):
     assert isinstance(dataset.wcs, gwcs.WCS)
     assert dataset.wcs.world_n_dim == 3
     assert dataset.wcs.pixel_n_dim == 3
+
+
+@pytest.fixture
+def wrap_object(mocker):
+
+    def wrap_object(target, attribute):
+        mock = mocker.MagicMock()
+        real_attribute = getattr(target, attribute)
+
+        def mocked_attribute(self, *args, **kwargs):
+            mock.__call__(*args, **kwargs)
+            return real_attribute(self, *args, **kwargs)
+
+        mocker.patch.object(target, attribute, mocked_attribute)
+
+        return mock
+
+    return wrap_object
+
+
+def test_loader_getitem_with_chunksize(eit_dataset_asdf_path, wrap_object):
+    chunksize = (32, 16)
+    with asdf.open(eit_dataset_asdf_path) as tree:
+        dataset = tree["dataset"]
+        dataset.files.basepath = rootdir / "EIT"
+        dataset.files._striped_external_array.chunksize = chunksize
+        oo = wrap_object(dataset.files._striped_external_array._loader, "__getitem__")
+        dataset._data = dataset.files._generate_array()
+        dataset.data.compute()
+
+    expected_call = call((slice(0, chunksize[0], None), slice(0, chunksize[1], None)))
+    assert expected_call in oo.mock_calls