add equal test method.

src/diffpy/srmise/tests/test_dataclusters.py

@@ -1,4 +1,5 @@
 import numpy as np
+import pytest
 
 from diffpy.srmise.dataclusters import DataClusters
 
@@ -10,3 +11,29 @@ def test_clear():
     # Perform the clear operation
     actual.clear()
     assert actual == expected
+
+
+@pytest.mark.parametrize(
+    "inputs, expected",
+    [
+        (
+            {
+                "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),
+        ),
+        (
+            {
+                "input_x": np.array([]),
+                "input_y": np.array([]),
+                "input_res": 0,
+            },
+            DataClusters(np.array([]), np.array([]), 0),
+        ),
+    ],
+)
+def test_equal(inputs, expected):
+    actual = DataClusters(x=inputs["input_x"], y=inputs["input_y"], res=inputs["input_res"])
+    assert actual == expected