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LGTM.

I would like to propose that instead of running the test container in the github action, it's started by the test setup system, using something like testcontainers. This reduces a hurdle in running the tests locally.

The following diff implements this:

diff --git a/src/doctor/rules/compression_test.py b/src/doctor/rules/compression_test.py
index b74d4a7..9b8f381 100644
--- a/src/doctor/rules/compression_test.py
+++ b/src/doctor/rules/compression_test.py
@@ -19,6 +19,7 @@ import unittest
 import psycopg2

 from psycopg2.extras import RealDictCursor
+from testcontainers.postgres import PostgresContainer
 from timescaledb import Hypertable

 from doctor.rules.compression import LinearSegmentBy, PointlessSegmentBy
@@ -34,15 +35,10 @@ class TestCompressionRules(unittest.TestCase):

     def setUp(self):
         """Set up unit tests for compression rules."""
-        user = os.getenv("PGUSER")
-        host = os.getenv("PGHOST")
-        port = os.getenv("PGPORT") or "5432"
-        dbname = os.getenv("PGDATABASE")
-        password = os.getenv("PGPASSWORD")
-        print(f"connecting to {host}:{port} database {dbname}")
-        self.__conn = psycopg2.connect(dbname=dbname, user=user, host=host,
-                                       password=password, port=port,
-                                       cursor_factory=RealDictCursor)
+        self.__container = PostgresContainer("timescale/timescaledb-ha:pg15", driver="default").start()
+        connstring = self.__container.get_connection_url().replace("+psycopg2", "")
+        print(f"connecting to {connstring}")
+        self.__conn = psycopg2.connect(connstring, cursor_factory=RealDictCursor)
         table = Hypertable("conditions", "time", {
                            'time': "timestamptz not null",
                            'device_id': "integer",
@@ -71,6 +67,7 @@ class TestCompressionRules(unittest.TestCase):
         with self.__conn.cursor() as cursor:
             cursor.execute("DROP TABLE conditions")
         self.__conn.commit()
+        self.__container.stop()

     def run_rule(self, rule):
         """Run rule and return messages."""

Seems reasonable to do, but then it might be useful to allow each test to pick the container. Some of the rules only works if you have a container that do not have TimescaleDB installed, so to check those, you need to pick a standard PostgreSQL image.

Tempted to push this and handle that as a separate PR, but going to investigate if this is straightforward to do and include in this PR.

Creating a good container support for test cases was more work then expected. Pushing this and taking this as a separate PR.