diff --git a/charms/slurmctld/tests/unit/test_charm.py b/charms/slurmctld/tests/unit/test_charm.py
index b6c9c93..353b3ff 100644
--- a/charms/slurmctld/tests/unit/test_charm.py
+++ b/charms/slurmctld/tests/unit/test_charm.py
@@ -62,6 +62,7 @@ def test_install_success(self, defer, *_) -> None:
         self.harness.charm._slurmctld.jwt.get.return_value = "=X="
         self.harness.charm._slurmctld.munge = Mock()
         self.harness.charm._slurmctld.munge.key.get.return_value = "=X="
+        self.harness.charm._slurmctld.exporter = Mock()
         self.harness.charm._slurmctld.service = Mock()
 
         self.harness.charm.on.install.emit()
diff --git a/test-requirements.txt b/test-requirements.txt
index 1ff6436..65736bd 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -6,3 +6,7 @@ pycryptodome==3.20.0
 slurmutils~=0.8.0
 dbus-fast>=1.90.2
 pyfakefs==5.7.1
+
+# `cos` dependencies
+cosl
+pydantic