add unit test

metadata.yaml

@@ -13,7 +13,7 @@ website:
 summary: A mongos operator charm
 series:
   - jammy
-# subordinate: true
+subordinate: true
 
 peers:
   router-peers:

tests/unit/__init__.py

@@ -0,0 +1,2 @@
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.

tests/unit/helpers.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+"""Helper functions for writing tests."""
+
+from typing import Callable
+from unittest.mock import patch
+
+
+def patch_network_get(private_address="10.1.157.116") -> Callable:
+    def network_get(*args, **kwargs) -> dict:
+        """Patch for the not-yet-implemented testing backend needed for `bind_address`.
+
+        This patch decorator can be used for cases such as:
+        self.model.get_binding(event.relation).network.bind_address
+        """
+        return {
+            "bind-addresses": [
+                {
+                    "mac-address": "",
+                    "interface-name": "",
+                    "addresses": [{"hostname": "", "value": private_address, "cidr": ""}],
+                }
+            ],
+            "bind-address": private_address,
+            "egress-subnets": ["10.152.183.65/32"],
+            "ingress-addresses": ["10.152.183.65"],
+        }
+
+    return patch("ops.testing._TestingModelBackend.network_get", network_get)

tests/unit/test_charm.py

@@ -0,0 +1,30 @@
+# Copyright 2023 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+import unittest
+from unittest.mock import patch
+
+from charms.operator_libs_linux.v1 import snap
+from ops.model import BlockedStatus
+from ops.testing import Harness
+
+from charm import MongosOperatorCharm
+
+from .helpers import patch_network_get
+
+
+class TestCharm(unittest.TestCase):
+    def setUp(self, *unused):
+        self.harness = Harness(MongosOperatorCharm)
+        self.addCleanup(self.harness.cleanup)
+        self.harness.begin()
+        self.peer_rel_id = self.harness.add_relation("router-peers", "router-peers")
+
+    @patch_network_get(private_address="1.1.1.1")
+    @patch("charm.snap.SnapCache")
+    @patch("subprocess.check_call")
+    def test_install_snap_packages_failure(self, _call, snap_cache):
+        """Test verifies that install hook fails when a snap error occurs."""
+        snap_cache.side_effect = snap.SnapError
+        self.harness.charm.on.install.emit()
+        self.assertTrue(isinstance(self.harness.charm.unit.status, BlockedStatus))

tox.ini

@@ -46,6 +46,21 @@ commands =
     ruff {[vars]all_path}
     black --check --diff {[vars]all_path}
 
+[testenv:unit]
+description = Run unit tests
+deps =
+    pytest
+    requests
+    pytest-mock
+    juju==3.2.0.1
+    coverage[toml]
+    parameterized
+    -r {tox_root}/requirements.txt
+commands =
+    coverage run --source={[vars]src_path} \
+        -m pytest -v --tb native -s {posargs} {[vars]tests_path}/unit
+    coverage report
+
 
 [testenv:static]
 description = Run static type checks