rework unit test to use pytest, add apt package install tests

src/service.py

@@ -117,7 +117,7 @@ def install(self) -> None:
             apt.update()
             apt.add_package("openjdk-17-jre")
             apt.add_package(AGENT_PACKAGE_NAME)
-        except (apt.PackageError, apt.PackageNotFoundError) as exc:
+        except (apt.PackageError, apt.PackageNotFoundError, apt.GPGKeyError) as exc:
             raise PackageInstallError("Error installing the agent package") from exc
 
     def restart(self) -> None:

tests/unit/conftest.py

@@ -0,0 +1,19 @@
+# Copyright 2024 Canonical Ltd.
+# See LICENSE file for licensing details.
+"""Fixtures for jenkins-agent charm tests."""
+
+
+import pytest
+from ops.testing import Harness
+
+from charm import JenkinsAgentCharm
+
+
+@pytest.fixture(scope="function", name="harness")
+def harness_fixture():
+    """Enable ops test framework harness."""
+    harness = Harness(JenkinsAgentCharm)
+
+    yield harness
+
+    harness.cleanup()

tests/unit/test_charm.py

@@ -6,14 +6,14 @@
 # pylint: disable=protected-access
 """Test for charm hooks."""
 
-import unittest
-import unittest.mock
-from unittest.mock import patch
+from unittest.mock import MagicMock
 
 import ops
 import ops.testing
+import pytest
 
 import charm_state
+import service
 from charm import JenkinsAgentCharm
 
 
@@ -29,58 +29,56 @@ def raise_exception(exception: Exception):
     raise exception
 
 
-class TestCharm(unittest.TestCase):
-    """Test class for unit testing."""
+def test___init___invalid_state(harness: ops.testing.Harness, monkeypatch: pytest.MonkeyPatch):
+    """
+    arrange: patched State.from_charm that raises an InvalidState Error.
+    act: when the JenkinsAgentCharm is initialized.
+    assert: The agent falls into BlockedStatus.
+    """
+    monkeypatch.setattr(
+        charm_state.State,
+        "from_charm",
+        MagicMock(side_effect=[charm_state.InvalidStateError("Invalid executor message")]),
+    )
 
-    def setUp(self):
-        """Initialize the test class."""
-        self.harness = ops.testing.Harness(JenkinsAgentCharm)
-        self.addCleanup(self.harness.cleanup)
+    harness.begin()
 
-    @patch(
-        "charm_state.State.from_charm",
-        side_effect=charm_state.InvalidStateError("Invalid executor message"),
-    )
-    def test___init___invalid_state(self, _):
-        """
-        arrange: patched State.from_charm that raises an InvalidState Error.
-        act: when the JenkinsAgentCharm is initialized.
-        assert: The agent falls into BlockedStatus.
-        """
-        self.harness.begin()
-
-        jenkins_charm: JenkinsAgentCharm = self.harness.charm
-        assert jenkins_charm.unit.status.name == ops.BlockedStatus.name
-        assert jenkins_charm.unit.status.message == "Invalid executor message"
-
-    @patch("service.JenkinsAgentService.restart")
-    @patch("service.JenkinsAgentService.is_active", return_value=True)
-    @patch("ops.UpgradeCharmEvent")
-    def test__on_upgrade_charm(self, _service_restart, _service_is_active, _upgrade_charm_event):
-        """
-        arrange: given a charm with patched agent service that is active.
-        act: when _on_upgrade_charm is called.
-        assert: The agent falls into waiting status with the correct message.
-        """
-        self.harness.begin()
-
-        jenkins_charm: JenkinsAgentCharm = self.harness.charm
-        jenkins_charm._on_upgrade_charm(_upgrade_charm_event)
-
-        assert jenkins_charm.unit.status.message == "Waiting for relation."
-        assert jenkins_charm.unit.status.name == ops.BlockedStatus.name
-
-    @patch("ops.ConfigChangedEvent")
-    @patch("ops.Model.get_relation")
-    def test__on_config_changed(self, _get_relation_mock, _config_changed_event):
-        """
-        arrange: given a charm with patched relation.
-        act: when _on_config_changed is called.
-        assert: The charm correctly updates the relation databag.
-        """
-        self.harness.begin()
-        jenkins_charm: JenkinsAgentCharm = self.harness.charm
-        jenkins_charm._on_config_changed(_config_changed_event)
-
-        agent_relation = _get_relation_mock.return_value
-        assert agent_relation.data[self.harness._unit_name].update.call_count == 1
+    jenkins_charm: JenkinsAgentCharm = harness.charm
+    assert jenkins_charm.unit.status.name == ops.BlockedStatus.name
+    assert jenkins_charm.unit.status.message == "Invalid executor message"
+
+
+def test__on_upgrade_charm(harness: ops.testing.Harness, monkeypatch: pytest.MonkeyPatch):
+    """
+    arrange: given a charm with patched agent service that is active.
+    act: when _on_upgrade_charm is called.
+    assert: The agent falls into waiting status with the correct message.
+    """
+    monkeypatch.setattr(service.JenkinsAgentService, "is_active", MagicMock(return_value=True))
+    monkeypatch.setattr(service.JenkinsAgentService, "restart", MagicMock())
+    harness.begin()
+
+    jenkins_charm: JenkinsAgentCharm = harness.charm
+    upgrade_charm_event = MagicMock(spec=ops.UpgradeCharmEvent)
+    jenkins_charm._on_upgrade_charm(upgrade_charm_event)
+
+    assert jenkins_charm.unit.status.message == "Waiting for relation."
+    assert jenkins_charm.unit.status.name == ops.BlockedStatus.name
+
+
+def test__on_config_changed(harness: ops.testing.Harness, monkeypatch: pytest.MonkeyPatch):
+    """
+    arrange: given a charm with patched relation.
+    act: when _on_config_changed is called.
+    assert: The charm correctly updates the relation databag.
+    """
+    harness.begin()
+    config_changed_event = MagicMock(spec=ops.ConfigChangedEvent)
+    get_relation_mock = MagicMock()
+    monkeypatch.setattr(ops.Model, "get_relation", get_relation_mock)
+
+    jenkins_charm: JenkinsAgentCharm = harness.charm
+    jenkins_charm._on_config_changed(config_changed_event)
+
+    agent_relation = get_relation_mock.return_value
+    assert agent_relation.data[harness._unit_name].update.call_count == 1

tests/unit/test_service.py

@@ -0,0 +1,40 @@
+# Copyright 2024 Canonical Ltd.
+# See LICENSE file for licensing details.
+"""Test for service interaction."""
+# pylint: disable=protected-access
+from unittest.mock import MagicMock
+
+import ops.testing
+import pytest
+from charms.operator_libs_linux.v0 import apt
+
+from charm import JenkinsAgentCharm
+
+
+@pytest.mark.parametrize(
+    "f,error_thrown",
+    [
+        ("import_key", apt.GPGKeyError),
+        ("add_package", apt.PackageError),
+        ("add_package", apt.PackageNotFoundError),
+    ],
+)
+def test_install_apt_package_gpg_key_error(
+    harness: ops.testing.Harness, monkeypatch: pytest.MonkeyPatch, f, error_thrown
+):
+    """
+    arrange: Harness with mocked apt module.
+    act: run _on_install hook with methods raising different errors.
+    assert: The charm should be in an error state.
+    """
+    harness.begin()
+    charm: JenkinsAgentCharm = harness.charm
+    monkeypatch.setattr(apt, "RepositoryMapping", MagicMock())
+    monkeypatch.setattr(apt, "import_key", MagicMock())
+    monkeypatch.setattr(apt, "update", MagicMock())
+    monkeypatch.setattr(apt, "add_package", MagicMock())
+
+    monkeypatch.setattr(apt, f, MagicMock(side_effect=[error_thrown]))
+
+    with pytest.raises(RuntimeError, match="Error installing the agent service"):
+        charm._on_install(MagicMock(spec=ops.InstallEvent))