Add $minN array element tests for null filtering and n validation

documentdb_tests/compatibility/tests/core/operator/expressions/array/minN-array-element/test_minN-array-element_n_validation.py

@@ -0,0 +1,31 @@
+"""
+Validation tests for $minN-array-element n argument.
+"""
+
+import pytest
+
+from documentdb_tests.framework.assertions import assertFailureCode
+from documentdb_tests.framework.error_codes import N_ARRAY_ELEMENT_NON_POSITIVE_N_ERROR
+from documentdb_tests.framework.executor import execute_command
+
+pytestmark = pytest.mark.aggregate
+
+
+def test_minN_array_element_rejects_zero_n(collection):
+    """Test $minN-array-element rejects n=0."""
+    collection.insert_one({"_id": 1, "values": [1, 2]})
+
+    result = execute_command(
+        collection,
+        {
+            "aggregate": collection.name,
+            "pipeline": [{"$project": {"minValues": {"$minN": {"n": 0, "input": "$values"}}}}],
+            "cursor": {},
+        },
+    )
+
+    assertFailureCode(
+        result,
+        N_ARRAY_ELEMENT_NON_POSITIVE_N_ERROR,
+        msg="$minN-array-element should reject n=0",
+    )

documentdb_tests/compatibility/tests/core/operator/expressions/array/minN-array-element/test_minN-array-element_null_filtering.py

@@ -0,0 +1,44 @@
+"""
+Compatibility tests for $minN-array-element null filtering behavior.
+
+Tests that $minN-array-element filters null values when n exceeds the number of
+available non-null values.
+"""
+
+import pytest
+
+from documentdb_tests.framework.assertions import assertSuccess
+from documentdb_tests.framework.executor import execute_command
+
+pytestmark = [pytest.mark.aggregate, pytest.mark.smoke]
+
+
+def test_minN_array_element_filters_null_values_when_n_exceeds_available_values(collection):
+    """Test $minN-array-element filters null values when n exceeds available values."""
+    collection.insert_many(
+        [
+            {"_id": 1, "values": [None, 8, 2, None, 5]},
+            {"_id": 2, "values": [None]},
+            {"_id": 3, "values": []},
+        ]
+    )
+
+    result = execute_command(
+        collection,
+        {
+            "aggregate": collection.name,
+            "pipeline": [{"$project": {"minValues": {"$minN": {"n": 5, "input": "$values"}}}}],
+            "cursor": {},
+        },
+    )
+
+    expected = [
+        {"_id": 1, "minValues": [2, 5, 8]},
+        {"_id": 2, "minValues": []},
+        {"_id": 3, "minValues": []},
+    ]
+    assertSuccess(
+        result,
+        expected,
+        msg="$minN-array-element should filter null values when n exceeds available values",
+    )

documentdb_tests/framework/error_codes.py

@@ -483,6 +483,7 @@
 MERGE_INTO_EMPTY_STRING_ERROR = 5786800
 MERGE_INTO_COLL_NULL_ERROR = 5786801
 N_ACCUMULATOR_MISSING_N_FIRSTN_FAMILY_ERROR = 5787906
+N_ARRAY_ELEMENT_NON_POSITIVE_N_ERROR = 5787908
 N_ACCUMULATOR_MISSING_N_TOPN_FAMILY_ERROR = 5788003
 GEO_NEAR_NEAR_REQUIRED_ERROR = 5860400
 GEO_NEAR_NEAR_TYPE_ERROR = 5860401