add test comment and corresponding tests to test files.

src/diffpy/srmise/tests/test_dataclusters.py

@@ -1,5 +1,5 @@
 from copy import copy
-
+import pytest
 import numpy as np
 
 from diffpy.srmise.dataclusters import DataClusters
@@ -32,3 +32,34 @@ def test___eq__():
             print(f"not-equal test failed on {attr_key}")
             assert not expected == actual
         attributes.update({attr_key: reset})
+
+# For reset clusters test, we have two test cases:
+# Precondition: DataClusters object should be a valid object.
+# Case (1): x and y are non-empty with positive res, reset_clusters would reset clusters to largest y arg
+# Case (2): x and y are empty with zero res, reset_clusters would reset clusters to an empty numpy arr
+@pytest.mark.parametrize(
+    "inputs, expected",
+    [
+        (
+            # case (1)
+            {
+                "input_x": np.array([1, 2, 3]),
+                "input_y": np.array([3, 2, 1]),
+                "input_res": 4,
+            },
+            DataClusters(np.array([1, 2, 3]), np.array([3, 2, 1]), 4),
+        ),
+        (
+            # case (2)
+            {
+                "input_x": np.array([]),
+                "input_y": np.array([]),
+                "input_res": 0,
+            },
+            DataClusters(np.array([]), np.array([]), 0),
+        ),
+    ],
+)
+def test_reset_clusters(inputs, expected):
+    actual = DataClusters(x=inputs["input_x"], y=inputs["input_y"], res=inputs["input_res"])
+    assert actual == expected