Add tests for empty-DF-with-columns and all-NaN create, prompt before cleanup

- test_get_no_results_with_select_preserves_columns: verifies empty result
  with select returns DataFrame with expected column names
- test_create_all_nan_rows_raises: verifies all-NaN rows raise ValueError
- prodev: cleanup now prompts user (Y/n) before deleting demo tables,
  matching the pattern in alternate_keys_upsert.py

Author: Saurabh Badenkal

examples/advanced/prodev_quick_start.py

@@ -120,8 +120,12 @@ def run_demo(client):
     # -- Step 5: Update and delete --
     step5_update_and_delete(client, task_ids, primary_name_col, primary_id_col)
 
-    # -- Step 6: Cleanup --
-    cleanup(client)
+    # -- Step 6: Cleanup (optional -- prompts before deleting) --
+    do_cleanup = input("\n6. Delete demo tables and cleanup? (Y/n): ").strip() or "y"
+    if do_cleanup.lower() in ("y", "yes"):
+        cleanup(client)
+    else:
+        print("[INFO] Tables kept for inspection.")
 
     print("\n" + "=" * 60)
     print("[OK] Pro-dev quick start demo complete!")

tests/unit/test_dataframe_operations.py

@@ -59,6 +59,21 @@ def test_get_no_results(self):
         self.assertIsInstance(df, pd.DataFrame)
         self.assertEqual(len(df), 0)
 
+    def test_get_no_results_with_select_preserves_columns(self):
+        """Empty result with select returns DataFrame with expected columns."""
+        self.client._odata._get_multiple.return_value = iter([])
+        df = self.client.dataframe.get("account", select=["name", "telephone1"])
+        self.assertIsInstance(df, pd.DataFrame)
+        self.assertEqual(len(df), 0)
+        self.assertListEqual(list(df.columns), ["name", "telephone1"])
+
+    def test_create_all_nan_rows_raises(self):
+        """DataFrame where all values are NaN raises ValueError."""
+        df = pd.DataFrame([{"name": None, "phone": None}])
+        with self.assertRaises(ValueError) as ctx:
+            self.client.dataframe.create("account", df)
+        self.assertIn("no non-null values", str(ctx.exception))
+
     def test_get_passes_all_params(self):
         """All OData parameters are forwarded to the underlying API call."""
         self.client._odata._get_multiple.return_value = iter([])