Add unit test for constant value expression

test/unit_tests/expression/test_constant.py

@@ -0,0 +1,39 @@
+# coding=utf-8
+# Copyright 2018-2023 EvaDB
+#
+# 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 unittest
+
+import pandas as pd
+
+from evadb.expression.constant_value_expression import ConstantValueExpression
+from evadb.models.storage.batch import Batch
+
+
+class ConstantExpressionsTest(unittest.TestCase):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def test_constant_without_input_relationship(self):
+        const_expr = ConstantValueExpression(1)
+        self.assertEqual([1], const_expr.evaluate(None).frames[0].tolist())
+
+    def test_constant_with_input_relationship(self):
+        const_expr = ConstantValueExpression(1)
+        input_size = 10
+        self.assertEqual(
+            [1] * input_size,
+            const_expr.evaluate(Batch(pd.DataFrame([0] * input_size)))
+            .frames[0]
+            .tolist(),
+        )