fix (tests): ensure that the leader is managing secrets (#356)

## Issue

As of ops 2.10+ `Harness` applies the same access controls to secrets as
Juju does in production. This causes tests to fail that were ignoring
these access restrictions (deliberately - they have docstrings that call
it out).

## Solution

Set the unit to be leader in each of the applicable tests. It might be
that you'd rather have tests for both cases, leader and (failing
appropriately) non-leader - I can adjust to do that if you prefer.

---------

Co-authored-by: Mehdi Bendriss <bendrissmehdi@gmail.com>

requirements.txt

@@ -4,7 +4,7 @@ cosl==0.0.7
 importlib-resources==5.10.2
 tenacity==8.1.0
 pymongo==4.3.3
-ops==2.4.1
+ops==2.12
 jsonschema==4.17.3
 cryptography==38.0.4
 pure-sasl==0.6.2
@@ -16,4 +16,4 @@ pyyaml==6.0.1
 zipp==3.11.0
 pyOpenSSL==22.1.0
 typing-extensions==4.5.0 
-parameterized==0.9.0
+parameterized==0.9.0

tests/unit/test_charm.py

@@ -9,7 +9,13 @@
 
 import pytest
 from charms.operator_libs_linux.v1 import snap
-from ops.model import ActiveStatus, BlockedStatus, MaintenanceStatus, WaitingStatus
+from ops.model import (
+    ActiveStatus,
+    BlockedStatus,
+    MaintenanceStatus,
+    ModelError,
+    WaitingStatus,
+)
 from ops.testing import Harness
 from parameterized import parameterized
 from pymongo.errors import ConfigurationError, ConnectionFailure, OperationFailure
@@ -720,8 +726,8 @@ def test_get_password(self):
         self.harness.charm.get_secret("unit", "non-existing-secret") is None
 
     def test_set_reset_existing_password_app(self):
-        """NOTE: currently ops.testing seems to allow for non-leader to set secrets too!"""
         self._setup_secrets()
+        self.harness.set_leader(True)
 
         # Getting current password
         self.harness.charm.set_secret("app", "monitor-password", "bla")
@@ -730,14 +736,24 @@ def test_set_reset_existing_password_app(self):
         self.harness.charm.set_secret("app", "monitor-password", "blablabla")
         assert self.harness.charm.get_secret("app", "monitor-password") == "blablabla"
 
+    def test_set_reset_existing_password_app_nonleader(self):
+        self._setup_secrets()
+        self.harness.set_leader(False)
+
+        # Getting current password
+        with self.assertRaises(ModelError):
+            self.harness.charm.set_secret("app", "monitor-password", "bla")
+
     @parameterized.expand([("app"), ("unit")])
     def test_set_secret_returning_secret_id(self, scope):
         secret_id = self.harness.charm.set_secret(scope, "somekey", "bla")
         assert re.match(f"mongodb.{scope}", secret_id)
 
     @parameterized.expand([("app"), ("unit")])
     def test_set_reset_new_secret(self, scope):
-        """NOTE: currently ops.testing seems to allow for non-leader to set secrets too!"""
+        if scope == "app":
+            self.harness.set_leader(True)
+
         # Getting current password
         self.harness.charm.set_secret(scope, "new-secret", "bla")
         assert self.harness.charm.get_secret(scope, "new-secret") == "bla"
@@ -750,6 +766,22 @@ def test_set_reset_new_secret(self, scope):
         self.harness.charm.set_secret(scope, "new-secret2", "blablabla")
         assert self.harness.charm.get_secret(scope, "new-secret2") == "blablabla"
 
+    def test_set_reset_new_secret_non_leader(self):
+        self.harness.set_leader(True)
+
+        # Getting current password
+        self.harness.charm.set_secret("app", "new-secret", "bla")
+        assert self.harness.charm.get_secret("app", "new-secret") == "bla"
+
+        # Reset new secret
+        self.harness.set_leader(False)
+        with self.assertRaises(ModelError):
+            self.harness.charm.set_secret("app", "new-secret", "blablabla")
+
+        # Set another new secret
+        with self.assertRaises(ModelError):
+            self.harness.charm.set_secret("app", "new-secret2", "blablabla")
+
     @parameterized.expand([("app"), ("unit")])
     def test_invalid_secret(self, scope):
         with self.assertRaises(TypeError):
@@ -760,8 +792,8 @@ def test_invalid_secret(self, scope):
 
     @pytest.mark.usefixtures("use_caplog")
     def test_delete_password(self):
-        """NOTE: currently ops.testing seems to allow for non-leader to remove secrets too!"""
         self._setup_secrets()
+        self.harness.set_leader(True)
 
         assert self.harness.charm.get_secret("app", "monitor-password")
         self.harness.charm.remove_secret("app", "monitor-password")
@@ -796,6 +828,13 @@ def test_delete_password(self):
                 in self._caplog.text
             )
 
+    def test_delete_password_non_leader(self):
+        self._setup_secrets()
+        self.harness.set_leader(False)
+        assert self.harness.charm.get_secret("app", "monitor-password")
+        with self.assertRaises(ModelError):
+            self.harness.charm.remove_secret("app", "monitor-password")
+
     @parameterized.expand([("app"), ("unit")])
     @patch("charm.MongodbOperatorCharm._connect_mongodb_exporter")
     def test_on_secret_changed(self, scope, connect_exporter):