Correctly export 3D patches

tests/test_roiset.py

@@ -138,8 +138,14 @@ class TestRoiSetMonoProducts(BaseTestRoiSetMonoProducts, unittest.TestCase):
         roiset = self._make_roi_set()
         files = roiset.export_patches(
             output_path / '3d_patches',
-            make_3d=True)
+            make_3d=True,
+            expanded=True
+        )
         self.assertGreaterEqual(len(files), 1)
+        for f in files:
+            acc = generate_file_accessor(f)
+            self.assertGreater(acc.nz, 1)
+
 
     def test_export_annotated_zstack(self):
         roiset = self._make_roi_set()