feat: API for asset sync (#19220)

* feat: API for asset sync

* Add unit tests.

* Improve tests

* Move files

* Add more tests

tests/unit_tests/conftest.py

@@ -14,9 +14,10 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-# pylint: disable=redefined-outer-name
+# pylint: disable=redefined-outer-name, import-outside-toplevel
 
-from typing import Iterator
+import importlib
+from typing import Any, Iterator
 
 import pytest
 from pytest_mock import MockFixture
@@ -25,11 +26,12 @@ from sqlalchemy.orm import sessionmaker
 from sqlalchemy.orm.session import Session
 
 from superset.app import SupersetApp
+from superset.extensions import appbuilder
 from superset.initialization import SupersetAppInitializer
 
 
-@pytest.fixture()
-def session() -> Iterator[Session]:
+@pytest.fixture
+def session(mocker: MockFixture) -> Iterator[Session]:
     """
     Create an in-memory SQLite session to test models.
     """
@@ -40,11 +42,18 @@ def session() -> Iterator[Session]:
     # flask calls session.remove()
     in_memory_session.remove = lambda: None
 
+    # patch session
+    mocker.patch(
+        "superset.security.SupersetSecurityManager.get_session",
+        return_value=in_memory_session,
+    )
+    mocker.patch("superset.db.session", in_memory_session)
+
     yield in_memory_session
 
 
-@pytest.fixture
-def app(mocker: MockFixture, session: Session) -> Iterator[SupersetApp]:
+@pytest.fixture(scope="module")
+def app() -> Iterator[SupersetApp]:
     """
     A fixture that generates a Superset app.
     """
@@ -52,20 +61,31 @@ def app(mocker: MockFixture, session: Session) -> Iterator[SupersetApp]:
 
     app.config.from_object("superset.config")
     app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite://"
-    app.config["FAB_ADD_SECURITY_VIEWS"] = False
+    app.config["TESTING"] = True
 
-    app_initializer = app.config.get("APP_INITIALIZER", SupersetAppInitializer)(app)
+    # ``superset.extensions.appbuilder`` is a singleton, and won't rebuild the
+    # routes when this fixture is called multiple times; we need to clear the
+    # registered views to ensure the initialization can happen more than once.
+    appbuilder.baseviews = []
+
+    app_initializer = SupersetAppInitializer(app)
     app_initializer.init_app()
 
-    # patch session
-    mocker.patch(
-        "superset.security.SupersetSecurityManager.get_session", return_value=session,
-    )
-    mocker.patch("superset.db.session", session)
+    # reload base views to ensure error handlers are applied to the app
+    with app.app_context():
+        import superset.views.base
+
+        importlib.reload(superset.views.base)
 
     yield app
 
 
+@pytest.fixture
+def client(app: SupersetApp) -> Any:
+    with app.test_client() as client:
+        yield client
+
+
 @pytest.fixture
 def app_context(app: SupersetApp) -> Iterator[None]:
     """