test(ISD-847): Add workaround to unit tests simulating charm initiali…

…zation after config-change event

src/charm.py

@@ -67,9 +67,6 @@ def _on_config_changed(self, event: ops.HookEvent) -> None:
             self.unit.status = ops.WaitingStatus("Waiting for pebble")
             return
         try:
-            self._charm_state = CharmState.from_charm(charm=self)
-            self._synapse = Synapse(charm_state=self._charm_state)
-            self._synapse.check_server_name(container)
             self.model.unit.status = ops.MaintenanceStatus("Configuring Synapse")
             self._synapse.execute_migrate_config(container)
         except (

tests/unit/conftest.py

@@ -3,7 +3,7 @@
 
 """pytest fixtures for the unit test."""
 
-# pylint: disable=too-few-public-methods
+# pylint: disable=too-few-public-methods, protected-access
 
 import typing
 import unittest.mock
@@ -165,6 +165,26 @@ def harness_server_name_configured_fixture(harness: Harness) -> Harness:
     return harness
 
 
+@pytest.fixture(name="harness_server_name_changed")
+def harness_server_name_changed_fixture(harness_server_name_configured: Harness) -> Harness:
+    """Ops testing framework harness fixture with server_name changed.
+
+    This is a workaround for the fact that Harness doesn't reinitialize the charm as expected.
+    Reference: https://github.com/canonical/operator/issues/736
+    """
+    harness = harness_server_name_configured
+    harness.disable_hooks()
+    harness._framework = ops.framework.Framework(
+        harness._storage, harness._charm_dir, harness._meta, harness._model
+    )
+    harness._charm = None
+    server_name_changed = "pebble-layer-1.synapse.com"
+    harness.update_config({"server_name": server_name_changed})
+    harness.enable_hooks()
+    harness.begin_with_initial_hooks()
+    return harness
+
+
 @pytest.fixture(name="container_mocked")
 def container_mocked_fixture(monkeypatch: pytest.MonkeyPatch) -> unittest.mock.MagicMock:
     """Mock container base to others fixtures."""

tests/unit/test_charm.py

@@ -114,32 +114,26 @@ def test_traefik_integration(harness_server_name_configured: Harness) -> None:
 
 
 @pytest.mark.parametrize("harness", [0], indirect=True)
-def test_server_name_change(harness_server_name_configured: Harness) -> None:
+def test_server_name_change(harness_server_name_changed: Harness) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: change to a different server_name.
     assert: Synapse charm should prevent the change with a BlockStatus.
     """
-    harness = harness_server_name_configured
-    server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
+    harness = harness_server_name_changed
     assert isinstance(harness.model.unit.status, ops.BlockedStatus)
     assert "server_name modification is not allowed" in str(harness.model.unit.status)
 
 
 @pytest.mark.parametrize("harness", [0], indirect=True)
-def test_reset_instance_action(harness_server_name_configured: Harness) -> None:
+def test_reset_instance_action(harness_server_name_changed: Harness) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: run reset-instance action.
     assert: Synapse charm should reset the instance.
     """
-    harness = harness_server_name_configured
+    harness = harness_server_name_changed
     harness.set_leader(True)
-    server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
-    assert isinstance(harness.model.unit.status, ops.BlockedStatus)
-    assert "server_name modification is not allowed" in str(harness.model.unit.status)
     event = unittest.mock.Mock()
     # Calling to test the action since is not possible calling via harness
     harness.charm._on_reset_instance_action(event)
@@ -149,18 +143,14 @@ def test_reset_instance_action(harness_server_name_configured: Harness) -> None:
 
 
 @pytest.mark.parametrize("harness", [1], indirect=True)
-def test_reset_instance_action_failed(harness_server_name_configured: Harness) -> None:
+def test_reset_instance_action_failed(harness_server_name_changed: Harness) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: change server_name and run reset-instance action.
     assert: Synapse charm should be blocked by error on migrate_config command.
     """
-    harness = harness_server_name_configured
+    harness = harness_server_name_changed
     harness.set_leader(True)
-    server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
-    assert isinstance(harness.model.unit.status, ops.BlockedStatus)
-    assert "server_name modification is not allowed" in str(harness.model.unit.status)
     event = unittest.mock.Mock()
     # Calling to test the action since is not possible calling via harness
     harness.charm._on_reset_instance_action(event)
@@ -172,19 +162,15 @@ def test_reset_instance_action_failed(harness_server_name_configured: Harness) -
 @pytest.mark.parametrize("harness", [0], indirect=True)
 def test_reset_instance_action_path_error_blocked(
     container_with_path_error_blocked: unittest.mock.MagicMock,
-    harness_server_name_configured: Harness,
+    harness_server_name_changed: Harness,
 ) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: change server_name and run reset-instance action.
     assert: Synapse charm should be blocked by error on remove_path.
     """
-    harness = harness_server_name_configured
+    harness = harness_server_name_changed
     harness.set_leader(True)
-    server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
-    assert isinstance(harness.model.unit.status, ops.BlockedStatus)
-    assert "server_name modification is not allowed" in str(harness.model.unit.status)
     harness.charm.unit.get_container = unittest.mock.MagicMock(
         return_value=container_with_path_error_blocked
     )
@@ -199,20 +185,17 @@ def test_reset_instance_action_path_error_blocked(
 @pytest.mark.parametrize("harness", [0], indirect=True)
 def test_reset_instance_action_path_error_pass(
     container_with_path_error_pass: unittest.mock.MagicMock,
-    harness_server_name_configured: Harness,
+    harness_server_name_changed: Harness,
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: change server_name and run reset-instance action.
     assert: Synapse charm should reset the instance.
     """
-    harness = harness_server_name_configured
+    harness = harness_server_name_changed
     harness.set_leader(True)
     server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
-    assert isinstance(harness.model.unit.status, ops.BlockedStatus)
-    assert "server_name modification is not allowed" in str(harness.model.unit.status)
     content = io.StringIO(f'server_name: "{server_name_changed}"')
     pull_mock = unittest.mock.MagicMock(return_value=content)
     monkeypatch.setattr(container_with_path_error_pass, "pull", pull_mock)
@@ -228,19 +211,14 @@ def test_reset_instance_action_path_error_pass(
 
 @pytest.mark.parametrize("harness", [0], indirect=True)
 def test_reset_instance_action_no_leader(
-    harness_server_name_configured: Harness,
+    harness_server_name_changed: Harness,
 ) -> None:
     """
     arrange: start the Synapse charm, set Synapse container to be ready and set server_name.
     act: change server_name and run reset-instance action.
     assert: Synapse charm should take no action if no leader.
     """
-    harness = harness_server_name_configured
-    harness.set_leader(True)
-    server_name_changed = "pebble-layer-1.synapse.com"
-    harness.update_config({"server_name": server_name_changed})
-    assert isinstance(harness.model.unit.status, ops.BlockedStatus)
-    assert "server_name modification is not allowed" in str(harness.model.unit.status)
+    harness = harness_server_name_changed
     harness.set_leader(False)
     event = unittest.mock.MagicMock()
     # Calling to test the action since is not possible calling via harness