Add unit tests for custom charm functionality

charm/tests/unit/test_charm.py

@@ -0,0 +1,37 @@
+# Copyright 2026 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+"""Unit tests for the cs.canonical.com charm's custom functionality."""
+
+import pathlib
+import sys
+
+CHARM_DIR = pathlib.Path(__file__).parents[2]
+sys.path.insert(0, str(CHARM_DIR / "lib"))
+sys.path.insert(0, str(CHARM_DIR / "src"))
+
+from ops import testing  # noqa: E402
+
+import charm  # noqa: E402
+
+
+class TestWorkloadVersion:
+    """Test workload version is set on appropriate events."""
+
+    def test_pebble_ready_sets_version(self):
+        """On pebble-ready, workload version is set to VERSION constant."""
+        ctx = testing.Context(charm.CsCanonicalComCharm)
+        container = testing.Container("flask-app", can_connect=True)
+        state = testing.State(containers={container}, leader=True)
+
+        state_out = ctx.run(ctx.on.pebble_ready(container), state)
+        assert state_out.workload_version == charm.VERSION
+
+    def test_update_status_sets_version(self):
+        """On update-status, workload version is refreshed."""
+        ctx = testing.Context(charm.CsCanonicalComCharm)
+        container = testing.Container("flask-app", can_connect=True)
+        state = testing.State(containers={container}, leader=True)
+
+        state_out = ctx.run(ctx.on.update_status(), state)
+        assert state_out.workload_version == charm.VERSION