Add rerelate test (adapted from Loki #139) (#259)

* Drop the remove-app bit

Co-authored-by: Simon Aronsson <[email protected]>

tests/integration/test_rerelate.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+# Copyright 2022 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+"""This test module tests prometheus charm response to related apps being removed and re-related.
+
+1. Deploy the charm under test and a related app, relate them and wait for them to become idle.
+2. Remove the relation.
+3. Re-add the relation.
+4. Remove the related application.
+5. Redeploy the related application and add the relation back again.
+"""
+
+import asyncio
+import logging
+from pathlib import Path
+
+import pytest
+import yaml
+from helpers import oci_image
+from pytest_operator.plugin import OpsTest
+
+logger = logging.getLogger(__name__)
+
+METADATA = yaml.safe_load(Path("./metadata.yaml").read_text())
+app_name = METADATA["name"]
+resources = {"prometheus-image": oci_image("./metadata.yaml", "prometheus-image")}
+tester_app_name = "prometheus-tester"
+tester_resources = {
+    "prometheus-tester-image": oci_image(
+        "./tests/integration/prometheus-tester/metadata.yaml",
+        "prometheus-tester-image",
+    )
+}
+
+
+async def test_setup_env(ops_test: OpsTest):
+    await ops_test.model.set_config({"logging-config": "<root>=WARNING; unit=DEBUG"})
+
+
+@pytest.mark.abort_on_fail
+async def test_build_and_deploy(ops_test: OpsTest, prometheus_charm, prometheus_tester_charm):
+    """Build the charm-under-test and deploy it together with related charms."""
+    await asyncio.gather(
+        ops_test.model.deploy(
+            prometheus_charm,
+            resources=resources,
+            application_name=app_name,
+            num_units=2,
+            trust=True,
+        ),
+        ops_test.model.deploy(
+            prometheus_tester_charm,
+            resources=tester_resources,
+            application_name=tester_app_name,
+        ),
+        ops_test.model.deploy(
+            "ch:alertmanager-k8s",
+            application_name="alertmanager",
+            channel="edge",
+        ),
+        ops_test.model.deploy(
+            "ch:grafana-k8s",
+            application_name="grafana",
+            channel="edge",
+        ),
+        ops_test.model.deploy(
+            "ch:grafana-agent-k8s",
+            application_name="grafana-agent",
+            channel="edge",
+        ),
+        # TODO: add traefik after fetch-lib (there are breaking changes)
+    )
+
+    await asyncio.gather(
+        ops_test.model.add_relation(app_name, tester_app_name),
+        ops_test.model.add_relation(app_name, "alertmanager"),
+        ops_test.model.add_relation(app_name, "grafana:grafana-source"),
+        ops_test.model.add_relation(app_name, "grafana-agent:send-remote-write"),
+    )
+    await ops_test.model.wait_for_idle(status="active", timeout=600)
+
+
+@pytest.mark.abort_on_fail
+async def test_remove_relation(ops_test: OpsTest):
+    await asyncio.gather(
+        ops_test.model.applications[app_name].remove_relation("metrics-endpoint", tester_app_name),
+        ops_test.model.applications[app_name].remove_relation("alertmanager", "alertmanager"),
+        ops_test.model.applications[app_name].remove_relation("grafana-source", "grafana"),
+        ops_test.model.applications[app_name].remove_relation(
+            "receive-remote-write", "grafana-agent"
+        ),
+    )
+    await ops_test.model.wait_for_idle(apps=[app_name], status="active", timeout=600)
+
+
+@pytest.mark.abort_on_fail
+async def test_rerelate(ops_test: OpsTest):
+    await asyncio.gather(
+        ops_test.model.add_relation(app_name, tester_app_name),
+        ops_test.model.add_relation(app_name, "alertmanager"),
+        ops_test.model.add_relation(app_name, "grafana:grafana-source"),
+        ops_test.model.add_relation(app_name, "grafana-agent:send-remote-write"),
+    )
+    await ops_test.model.wait_for_idle(status="active", timeout=600)