Add stdDevPop, stdDevSamp window operator and setWindowFields stage tests

documentdb_tests/compatibility/tests/core/operator/stages/setWindowFields/test_setWindowFields_multi_output.py

@@ -0,0 +1,135 @@
+"""
+Tests for $setWindowFields multi-output behavior.
+
+These are operator-agnostic — they test the stage's ability to handle
+multiple output fields with different accumulators and window specs.
+
+Covers: multiple different operators in one output clause, same operator
+with different window specs, and output field that overwrites _id.
+"""
+
+from documentdb_tests.framework.assertions import assertSuccess
+from documentdb_tests.framework.executor import execute_command
+
+
+def test_mixed_operators_multi_output(collection):
+    """Multiple different operators ($sum + $avg + $count) in one output clause."""
+    docs = [
+        {"_id": 1, "partition": "A", "value": 10},
+        {"_id": 2, "partition": "A", "value": 20},
+        {"_id": 3, "partition": "A", "value": 30},
+    ]
+    collection.insert_many(docs)
+    result = execute_command(
+        collection,
+        {
+            "aggregate": collection.name,
+            "pipeline": [
+                {
+                    "$setWindowFields": {
+                        "partitionBy": "$partition",
+                        "sortBy": {"_id": 1},
+                        "output": {
+                            "total": {
+                                "$sum": "$value",
+                                "window": {"documents": ["unbounded", "unbounded"]},
+                            },
+                            "avg": {
+                                "$avg": "$value",
+                                "window": {"documents": ["unbounded", "unbounded"]},
+                            },
+                            "cnt": {
+                                "$count": {},
+                                "window": {"documents": ["unbounded", "unbounded"]},
+                            },
+                        },
+                    }
+                }
+            ],
+            "cursor": {},
+        },
+    )
+    expected = [
+        {"_id": 1, "partition": "A", "value": 10, "total": 60, "avg": 20.0, "cnt": 3},
+        {"_id": 2, "partition": "A", "value": 20, "total": 60, "avg": 20.0, "cnt": 3},
+        {"_id": 3, "partition": "A", "value": 30, "total": 60, "avg": 20.0, "cnt": 3},
+    ]
+    assertSuccess(result, expected, msg="mixed operators in one output clause")
+
+
+def test_same_operator_different_windows(collection):
+    """Same operator ($sum) with different window specs in one output clause."""
+    docs = [
+        {"_id": 1, "partition": "A", "value": 10},
+        {"_id": 2, "partition": "A", "value": 20},
+        {"_id": 3, "partition": "A", "value": 30},
+    ]
+    collection.insert_many(docs)
+    result = execute_command(
+        collection,
+        {
+            "aggregate": collection.name,
+            "pipeline": [
+                {
+                    "$setWindowFields": {
+                        "partitionBy": "$partition",
+                        "sortBy": {"_id": 1},
+                        "output": {
+                            "cumulative": {
+                                "$sum": "$value",
+                                "window": {"documents": ["unbounded", "current"]},
+                            },
+                            "whole": {
+                                "$sum": "$value",
+                                "window": {"documents": ["unbounded", "unbounded"]},
+                            },
+                        },
+                    }
+                }
+            ],
+            "cursor": {},
+        },
+    )
+    expected = [
+        {"_id": 1, "partition": "A", "value": 10, "cumulative": 10, "whole": 60},
+        {"_id": 2, "partition": "A", "value": 20, "cumulative": 30, "whole": 60},
+        {"_id": 3, "partition": "A", "value": 30, "cumulative": 60, "whole": 60},
+    ]
+    assertSuccess(result, expected, msg="same operator with different windows in one output")
+
+
+def test_output_field_name_id(collection):
+    """Output field named '_id' overwrites original document _id."""
+    docs = [
+        {"_id": 1, "partition": "A", "value": 10},
+        {"_id": 2, "partition": "A", "value": 20},
+        {"_id": 3, "partition": "A", "value": 30},
+    ]
+    collection.insert_many(docs)
+    result = execute_command(
+        collection,
+        {
+            "aggregate": collection.name,
+            "pipeline": [
+                {
+                    "$setWindowFields": {
+                        "partitionBy": "$partition",
+                        "sortBy": {"_id": 1},
+                        "output": {
+                            "_id": {
+                                "$sum": "$value",
+                                "window": {"documents": ["unbounded", "unbounded"]},
+                            }
+                        },
+                    }
+                }
+            ],
+            "cursor": {},
+        },
+    )
+    expected = [
+        {"_id": 60, "partition": "A", "value": 10},
+        {"_id": 60, "partition": "A", "value": 20},
+        {"_id": 60, "partition": "A", "value": 30},
+    ]
+    assertSuccess(result, expected, msg="output field _id overwrites document _id")