refactor(tests): decouple unittests from integration tests (#15473)

* refactor move all tests to be under integration_tests package

* refactor decouple unittests from integration tests - commands

* add unit_tests package

* fix celery_tests.py

* fix wrong FIXTURES_DIR value

tests/integration_tests/db_engine_specs/base_tests.py

@@ -0,0 +1,52 @@
+# 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.
+# isort:skip_file
+from datetime import datetime
+from typing import Tuple, Type
+
+from tests.integration_tests.test_app import app
+from tests.integration_tests.base_tests import SupersetTestCase
+from superset.db_engine_specs.base import BaseEngineSpec
+from superset.models.core import Database
+from superset.utils.core import GenericDataType
+
+
+class TestDbEngineSpec(SupersetTestCase):
+    def sql_limit_regex(
+        self,
+        sql,
+        expected_sql,
+        engine_spec_class=BaseEngineSpec,
+        limit=1000,
+        force=False,
+    ):
+        main = Database(database_name="test_database", sqlalchemy_uri="sqlite://")
+        limited = engine_spec_class.apply_limit_to_sql(sql, limit, main, force)
+        self.assertEqual(expected_sql, limited)
+
+
+def assert_generic_types(
+    spec: Type[BaseEngineSpec],
+    type_expectations: Tuple[Tuple[str, GenericDataType], ...],
+) -> None:
+    for type_str, expected_type in type_expectations:
+        column_spec = spec.get_column_spec(type_str)
+        assert column_spec is not None
+        actual_type = column_spec.generic_type
+        assert (
+            actual_type == expected_type
+        ), f"{type_str} should be {expected_type.name} but is {actual_type.name}"