diff --git a/lib/charms/observability_libs/v1/cert_handler.py b/lib/charms/observability_libs/v1/cert_handler.py
index bb892f9..78be36f 100644
--- a/lib/charms/observability_libs/v1/cert_handler.py
+++ b/lib/charms/observability_libs/v1/cert_handler.py
@@ -283,7 +283,7 @@ def __init__(
         peer_relation_name: str = "peers",
         cert_subject: Optional[str] = None,
         sans: Optional[List[str]] = None,
-        refresh_events: List[BoundEvent] = [],
+        refresh_events: Optional[List[BoundEvent]] = None,
     ):
         """CertHandler is used to wrap TLS Certificates management operations for charms.
 
@@ -360,8 +360,9 @@ def __init__(
             self._on_upgrade_charm,
         )
 
-        for ev in refresh_events:
-            self.framework.observe(ev, self._on_refresh_event)
+        if refresh_events:
+            for ev in refresh_events:
+                self.framework.observe(ev, self._on_refresh_event)
 
     def _on_refresh_event(self, _):
         """Replace the latest current CSR with a new one if there are any CSR changes.
diff --git a/tox.ini b/tox.ini
index e7f1122..060c63e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,6 +26,11 @@ passenv =
   HTTP_PROXY
   HTTPS_PROXY
   NO_PROXY
+allowlist_externals = charmcraft
+commands =
+    # update all charm libs
+    charmcraft fetch-lib charms.tls_certificates_interface.v3.tls_certificates
+    charmcraft fetch-lib charms.tls_certificates_interface.v2.tls_certificates
 
 [testenv:fmt]
 description = Apply coding style standards to code
@@ -96,10 +101,7 @@ commands =
     pytest -v --tb native --log-cli-level=INFO -s {posargs} {toxinidir}/tests/integration
 
 [testenv:scenario]
-description = Scenario tests (CI satisfaction placeholder)
-
-[testenv:scenario-manual]
-description = Scenario tests (manual only: GH runner does not like charmcraft fetch-lib)
+description = Scenario tests
 deps =
     pytest
     ops-scenario
@@ -110,6 +112,6 @@ allowlist_externals =
     charmcraft
     rm
 commands =
-    charmcraft fetch-lib charms.tls_certificates_interface.v2.tls_certificates
+    {[testenv]commands}
     pytest -v --tb native {[vars]tst_path}/scenario --log-cli-level=INFO -s {posargs}
     rm -rf ./lib/charms/tls_certificates_interface