test: Add slice op cross validation testing (#1837)

Author: TrevorBergeron

bigframes/session/polars_executor.py

@@ -31,6 +31,7 @@
     nodes.OrderByNode,
     nodes.ReversedNode,
     nodes.SelectionNode,
+    nodes.SliceNode,
 )
 
 _COMPATIBLE_SCALAR_OPS = ()

tests/system/small/engines/test_slicing.py

@@ -0,0 +1,56 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from bigframes.core import array_value, nodes
+from bigframes.session import polars_executor
+from bigframes.testing.engine_utils import assert_equivalence_execution
+
+pytest.importorskip("polars")
+
+# Polars used as reference as its fast and local. Generally though, prefer gbq engine where they disagree.
+REFERENCE_ENGINE = polars_executor.PolarsExecutor()
+
+
+@pytest.mark.parametrize("engine", ["polars", "bq"], indirect=True)
+@pytest.mark.parametrize(
+    ("start", "stop", "step"),
+    [
+        (1, None, None),
+        (None, 4, None),
+        (None, None, 2),
+        (None, 50_000_000_000, 1),
+        (5, 4, None),
+        (3, None, 2),
+        (1, 7, 2),
+        (1, 7, 50_000_000_000),
+        (-1, -7, -2),
+        (None, -7, -2),
+        (-1, None, -2),
+        (-7, -1, 2),
+        (-7, -1, None),
+        (-7, 7, None),
+        (7, -7, -2),
+    ],
+)
+def test_engines_slice(
+    scalars_array_value: array_value.ArrayValue,
+    engine,
+    start,
+    stop,
+    step,
+):
+    node = nodes.SliceNode(scalars_array_value.node, start, stop, step)
+    assert_equivalence_execution(node, REFERENCE_ENGINE, engine)