Add $indexStats stage tests

documentdb_tests/compatibility/tests/core/operator/stages/indexStats/test_indexStats_collection_types.py

@@ -0,0 +1,83 @@
+"""Tests for $indexStats collection type behavior."""
+
+from __future__ import annotations
+
+import pytest
+from pymongo.collection import Collection
+
+from documentdb_tests.compatibility.tests.core.operator.stages.indexStats.utils.indexStats_test_case import (  # noqa: E501
+    IndexStatsTestCase,
+    prepare_collection,
+)
+from documentdb_tests.framework.assertions import assertResult
+from documentdb_tests.framework.executor import execute_command
+from documentdb_tests.framework.parametrize import pytest_params
+from documentdb_tests.framework.target_collection import (
+    CappedCollection,
+    TimeseriesCollection,
+    ViewCollection,
+)
+
+# Property [Collection Existence]: $indexStats handles non-existent, empty,
+# and special collection types.
+COLLECTION_TYPE_TESTS: list[IndexStatsTestCase] = [
+    IndexStatsTestCase(
+        id="nonexistent_collection",
+        docs=None,
+        pipeline=[{"$indexStats": {}}, {"$count": "n"}],
+        expected=[],
+        msg="Non-existent collection should return 0 documents",
+    ),
+    IndexStatsTestCase(
+        id="empty_collection",
+        docs=[],
+        pipeline=[{"$indexStats": {}}, {"$count": "n"}],
+        expected=[{"n": 1}],
+        msg="Empty collection should return 1 document for the _id index",
+    ),
+    IndexStatsTestCase(
+        id="capped_collection",
+        target_collection=CappedCollection(),
+        docs=[],
+        pipeline=[{"$indexStats": {}}, {"$match": {"name": "_id_"}}, {"$count": "n"}],
+        expected=[{"n": 1}],
+        msg="Capped collection should report the _id index",
+    ),
+    IndexStatsTestCase(
+        id="timeseries_collection",
+        target_collection=TimeseriesCollection(),
+        docs=[],
+        pipeline=[{"$indexStats": {}}, {"$count": "n"}],
+        expected=[{"n": 1}],
+        msg="Time series collection should report at least one index",
+    ),
+    IndexStatsTestCase(
+        id="view_collection",
+        target_collection=ViewCollection(),
+        docs=[],
+        pipeline=[{"$indexStats": {}}, {"$match": {"name": "_id_"}}, {"$count": "n"}],
+        expected=[{"n": 1}],
+        msg="View should report the underlying collection's _id index",
+    ),
+]
+
+
+@pytest.mark.aggregate
+@pytest.mark.parametrize("test_case", pytest_params(COLLECTION_TYPE_TESTS))
+def test_indexStats_collection_types(collection: Collection, test_case: IndexStatsTestCase):
+    """Test $indexStats on various collection types."""
+    coll = prepare_collection(collection, test_case)
+    result = execute_command(
+        coll,
+        {
+            "aggregate": coll.name,
+            "pipeline": test_case.pipeline,
+            "cursor": {},
+        },
+    )
+    assertResult(
+        result,
+        expected=test_case.expected,
+        error_code=test_case.error_code,
+        msg=test_case.msg,
+    )