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/importexport/commands_tests.py

@@ -0,0 +1,48 @@
+# 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 unittest.mock import patch
+
+import yaml
+from freezegun import freeze_time
+
+from superset import security_manager
+from superset.databases.commands.export import ExportDatabasesCommand
+from superset.utils.core import get_example_database
+from tests.integration_tests.base_tests import SupersetTestCase
+
+
+class TestExportModelsCommand(SupersetTestCase):
+    @patch("superset.security.manager.g")
+    def test_export_models_command(self, mock_g):
+        """Make sure metadata.yaml has the correct content."""
+        mock_g.user = security_manager.find_user("admin")
+
+        example_db = get_example_database()
+
+        with freeze_time("2020-01-01T00:00:00Z"):
+            command = ExportDatabasesCommand([example_db.id])
+            contents = dict(command.run())
+
+        metadata = yaml.safe_load(contents["metadata.yaml"])
+        assert metadata == (
+            {
+                "version": "1.0.0",
+                "type": "Database",
+                "timestamp": "2020-01-01T00:00:00+00:00",
+            }
+        )