TST: Add a test to check order invariance

Check the label ordering does not cause any issues

Author: bashtage

pandas/tests/io/test_stata.py

@@ -1969,3 +1969,17 @@ def test_iterator_errors(dirpath):
     with pytest.raises(ValueError, match="chunksize must be set to a positive"):
         with StataReader(dta_file) as reader:
             reader.__next__()
+
+
+def test_iterator_value_labels():
+    # GH 31544
+    values = ["c_label", "b_label"] + ["a_label"] * 500
+    df = DataFrame({f"col{k}": pd.Categorical(values, ordered=True) for k in range(2)})
+    with tm.ensure_clean() as path:
+        df.to_stata(path, write_index=False)
+        reader = pd.read_stata(path, chunksize=100)
+        expected = pd.Index(["a_label", "b_label", "c_label"], dtype="object")
+        for j, chunk in enumerate(reader):
+            for i in range(2):
+                tm.assert_index_equal(chunk.dtypes[i].categories, expected)
+            tm.assert_frame_equal(chunk, df.iloc[j * 100 : (j + 1) * 100])