test: add unit tests for config and main modules (#25)

* chore(deps): add pytest and pytest-mock to requirements

* test: add pytest configuration and shared test fixtures

Add root conftest.py to handle module-level import side effects
(sys.argv sanitization, Docker client mocking), pytest.ini with
test paths config, and shared fixtures for mock Docker client,
config, and logger.

* test(config): add unit tests for configuration module

Cover flatten_keys, merge_dicts, load_config defaults, environment
variable overrides, CLI argument overrides, and init_loggers.

* test(main): add unit tests for core logic functions

Cover create_docker_client, update_container_cache, is_traefik_running,
connect/disconnect_traefik_to_network, and connect_to_all_relevant_networks.

* test(main): add unit tests for event monitoring

Cover start/stop/die events with and without labels, Traefik start
event triggering full reconnection, and non-container event filtering.

* ci: add test workflow for pull requests

Run pytest on every PR targeting main and on pushes to main.

* ci: add minimal permissions to test workflow

Restrict GITHUB_TOKEN to read-only contents access as flagged
by code scanning.

Author: obeone

.github/workflows/test.yml

@@ -0,0 +1,28 @@
+name: Tests
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: pip install -r requirements.txt
+
+      - name: Run tests
+        run: pytest tests/ -v --tb=short

conftest.py

@@ -0,0 +1,26 @@
+"""
+Root-level conftest.py for pytest.
+
+Patches sys.argv and docker.DockerClient early so that module-level
+initialization in config.py and main.py does not fail during test
+collection (parse_args reading pytest args, DockerClient connecting
+to a real Docker socket).
+"""
+
+import sys
+from unittest.mock import MagicMock
+
+# config.py calls parse_args() at module level, which reads sys.argv.
+# When running under pytest, sys.argv contains pytest args that config.py
+# does not recognize, causing a sys.exit(1). We sanitize sys.argv here
+# so the initial module import succeeds cleanly.
+_original_argv = sys.argv
+sys.argv = [sys.argv[0]]
+
+# main.py calls create_docker_client(config) at module level (line 43),
+# which instantiates docker.DockerClient and connects to the Docker socket.
+# We patch DockerClient before main.py is imported so no real connection
+# is attempted during test collection.
+import docker  # noqa: E402
+
+docker.DockerClient = MagicMock

pytest.ini

@@ -0,0 +1,5 @@
+[pytest]
+testpaths = tests
+python_files = test_*.py
+python_classes = Test*
+python_functions = test_*

requirements.txt

@@ -1,3 +1,5 @@
 docker==7.1.0
 coloredlogs==15.0.1
 PyYAML==6.0.1
+pytest==8.4.2
+pytest-mock==3.14.0

tests/__init__.py

@@ -0,0 +1,94 @@
+"""
+Shared pytest fixtures for the auto_docker_proxy test suite.
+
+Provides mock Docker client, configuration, and logger fixtures
+to isolate tests from real Docker daemon and filesystem dependencies.
+"""
+
+import sys
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from config import (
+    Config,
+    DockerConfig,
+    DockerTLSConfig,
+    LogLevelConfig,
+    TLSCertificateConfig,
+    TraefikConfig,
+)
+
+
+def make_test_config(**overrides):
+    """
+    Build a Config NamedTuple with sensible test defaults.
+
+    Parameters
+    ----------
+    overrides : dict
+        Keyword arguments whose keys match Config field paths.
+        Currently unused but kept for future extensibility.
+
+    Returns
+    -------
+    Config
+        A fully populated Config instance suitable for unit tests.
+    """
+    tls = DockerTLSConfig(
+        enabled=False,
+        verify=TLSCertificateConfig(file="/path/to/ca.pem"),
+        cert=TLSCertificateConfig(file="/path/to/cert.pem"),
+        key=TLSCertificateConfig(file="/path/to/key.pem"),
+    )
+    docker = DockerConfig(host="unix:///var/run/docker.sock", tls=tls)
+    log_level = LogLevelConfig(general="INFO", application="DEBUG")
+    traefik = TraefikConfig(
+        containerName="traefik",
+        monitoredLabel="^traefik.enable$",
+        networkLabel="traefik.docker.network",
+    )
+    return Config(docker=docker, logLevel=log_level, traefik=traefik)
+
+
+@pytest.fixture
+def mock_docker_client():
+    """
+    Patch ``main.client`` with a MagicMock so no real Docker daemon is needed.
+
+    Yields
+    ------
+    MagicMock
+        The mock object replacing ``main.client``.
+    """
+    with patch("main.client") as mock_client:
+        yield mock_client
+
+
+@pytest.fixture
+def mock_config():
+    """
+    Patch ``main.config`` with a realistic test Config NamedTuple.
+
+    Yields
+    ------
+    Config
+        The test configuration injected into ``main.config``.
+    """
+    cfg = make_test_config()
+    with patch("main.config", cfg):
+        yield cfg
+
+
+@pytest.fixture
+def mock_logger():
+    """
+    Patch ``main.app_logger`` with a MagicMock to capture log calls.
+
+    Yields
+    ------
+    MagicMock
+        The mock object replacing ``main.app_logger``.
+    """
+    with patch("main.app_logger") as mock_log:
+        yield mock_log