global port number, _configure, and move to scenario

src/charm.py

@@ -24,13 +24,18 @@ def __init__(self, framework: ops.Framework):
         self.container = self.unit.get_container("gocert")
         self.tls = TLSCertificatesProvidesV3(self, relationship_name="certificates")
 
-        framework.observe(self.on["gocert"].pebble_ready, self._on_gocert_pebble_ready)
+        self.port = 2111
+
+        framework.observe(self.on["gocert"].pebble_ready, self._configure)
+        framework.observe(self.on.config_changed, self._configure)
+
+        framework.observe(self.on.collect_unit_status, self._on_collect_status)
         framework.observe(self.on["gocert"].pebble_custom_notice, self._on_gocert_notify)
         framework.observe(self.tls.on.certificate_creation_request, self._on_new_certificate)
-        framework.observe(self.on.config_changed, self._on_config_changed)
-        framework.observe(self.on.collect_unit_status, self._on_collect_status)
 
-    def _on_gocert_pebble_ready(self, event: ops.PebbleReadyEvent):
+    def _configure(self, event: ops.EventBase):
+        if not self.container.can_connect():
+            return
         try:
             self.container.pull("/etc/config/config.yaml")
         except ops.pebble.PathError:
@@ -50,7 +55,7 @@ def _on_collect_status(self, event: ops.CollectStatusEvent):
     def _on_new_certificate(self, event: CertificateCreationRequestEvent):
         csr = event.certificate_signing_request
         requests.post(
-            url="https://localhost:2111/api/v1/certificate_requests",
+            url=f"https://localhost:{self.port}/api/v1/certificate_requests",
             data=csr,
             headers={"Content-Type": "text/plain"},
             verify=False,
@@ -76,9 +81,6 @@ def _on_gocert_notify(self, event: ops.PebbleCustomNoticeEvent):
                             relation_id=relation.id,
                         )
 
-    def _on_config_changed(self, event: ops.ConfigChangedEvent):
-        self.unit.status = ops.ActiveStatus()
-
     @property
     def _pebble_layer(self) -> ops.pebble.LayerDict:
         """Return a dictionary representing a Pebble layer."""

test-requirements.txt

@@ -0,0 +1 @@
+ops-scenario

tests/unit/test_charm.py

@@ -5,13 +5,14 @@
 import ops.testing
 import pytest
 from charm import GocertCharm
+from scenario import Context, Event, State
 
 
 class TestCharm:
     @pytest.fixture(scope="function", autouse=True)
-    def setUp(self):
-        self.harness = ops.testing.Harness(GocertCharm)
+    def context(self):
+        yield Context(GocertCharm)
 
-    def test_start_charm(self):
-        self.harness.begin_with_initial_hooks()
-        assert self.harness.model.unit.status == ops.ActiveStatus()
+    def test_start_charm(self, context):
+        out = context.run(Event("start"), State())
+        assert out.unit_status == ops.ActiveStatus()

tox.ini

@@ -46,6 +46,7 @@ deps =
     pytest
     coverage[toml]
     -r {tox_root}/requirements.txt
+    -r {tox_root}/test-requirements.txt
 commands =
     coverage run --source={[vars]src_path} \
                  -m pytest \