Split up tests/db_engine_test.py (#8449)

* Split up db_engine_specs_test.py into a number of targeted files

* Remove db_engine_specs_test.py

* isort

tests/db_engine_specs/oracle_tests.py

@@ -0,0 +1,36 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+from sqlalchemy import column
+from sqlalchemy.dialects import oracle
+
+from superset.db_engine_specs.oracle import OracleEngineSpec
+from tests.db_engine_specs.base_tests import DbEngineSpecTestCase
+
+
+class OracleTestCase(DbEngineSpecTestCase):
+    def test_oracle_sqla_column_name_length_exceeded(self):
+        col = column("This_Is_32_Character_Column_Name")
+        label = OracleEngineSpec.make_label_compatible(col.name)
+        self.assertEqual(label.quote, True)
+        label_expected = "3b26974078683be078219674eeb8f5"
+        self.assertEqual(label, label_expected)
+
+    def test_oracle_time_expression_reserved_keyword_1m_grain(self):
+        col = column("decimal")
+        expr = OracleEngineSpec.get_timestamp_expr(col, None, "P1M")
+        result = str(expr.compile(dialect=oracle.dialect()))
+        self.assertEqual(result, "TRUNC(CAST(\"decimal\" as DATE), 'MONTH')")