test(ci): add coverage for static-checks

Runs mypy and ruff. Add basic test.

- Update pyproject.toml dependencies groups
  - PDM can use top-level [dependency-groups] (PEP 735), support was added in pdm 2.20.0 (October 2024)
- Fix Ruff warnings

tests/test_cli.py

@@ -0,0 +1,95 @@
+from types import SimpleNamespace
+
+import mpd_now_playable.cli as cli
+
+
+def test_main_help_prints_usage(monkeypatch, capsys) -> None:
+	monkeypatch.setattr(cli.sys, "argv", ["mpd-now-playable", "--help"])
+
+	def fail_load() -> None:
+		raise AssertionError("loadConfig should not run for --help")
+
+	monkeypatch.setattr(cli, "loadConfig", fail_load)
+
+	cli.main()
+	output = capsys.readouterr().out
+
+	assert "Usage: mpd-now-playable [OPTIONS]" in output
+	assert "-h, --help" in output
+	assert "-v, --version" in output
+
+
+def test_main_version_prints_version(monkeypatch, capsys) -> None:
+	monkeypatch.setattr(cli.sys, "argv", ["mpd-now-playable", "--version"])
+
+	def fail_load() -> None:
+		raise AssertionError("loadConfig should not run for --version")
+
+	monkeypatch.setattr(cli, "loadConfig", fail_load)
+
+	cli.main()
+	output = capsys.readouterr().out
+
+	assert output.strip() == f"mpd-now-playable v{cli.__version__}"
+
+
+def test_main_starts_listener_and_receivers(monkeypatch) -> None:
+	receiver_cfg_1 = SimpleNamespace(kind="websockets")
+	receiver_cfg_2 = SimpleNamespace(kind="websockets")
+	config = SimpleNamespace(
+		cache="memory://",
+		mpd=SimpleNamespace(host="127.0.0.1", port=6600),
+		receivers=(receiver_cfg_1, receiver_cfg_2),
+	)
+
+	listener = object()
+	receiver_1 = object()
+	receiver_2 = object()
+	fake_coroutine = object()
+
+	seen = {}
+
+	def fake_load_config() -> SimpleNamespace:
+		return config
+
+	def fake_listener_ctor(cache: str) -> object:
+		seen["cache"] = cache
+		return listener
+
+	def fake_construct_receiver(rcfg: SimpleNamespace) -> object:
+		if rcfg is receiver_cfg_1:
+			return receiver_1
+		if rcfg is receiver_cfg_2:
+			return receiver_2
+		raise AssertionError(f"Unexpected receiver config: {rcfg!r}")
+
+	class FakeLoopFactory:
+		@staticmethod
+		def make_loop() -> object:
+			return object()
+
+	def fake_choose_loop_factory(receivers: tuple[object, ...]) -> type[FakeLoopFactory]:
+		seen["receivers"] = receivers
+		return FakeLoopFactory
+
+	def fake_listen(cfg: SimpleNamespace, lst: object, receivers: tuple[object, ...]) -> object:
+		seen["listen_args"] = (cfg, lst, receivers)
+		return fake_coroutine
+
+	def fake_run(coro: object, *, loop_factory: object, debug: bool) -> None:
+		seen["run"] = (coro, loop_factory, debug)
+
+	monkeypatch.setattr(cli.sys, "argv", ["mpd-now-playable"])
+	monkeypatch.setattr(cli, "loadConfig", fake_load_config)
+	monkeypatch.setattr(cli, "MpdStateListener", fake_listener_ctor)
+	monkeypatch.setattr(cli, "construct_receiver", fake_construct_receiver)
+	monkeypatch.setattr(cli, "choose_loop_factory", fake_choose_loop_factory)
+	monkeypatch.setattr(cli, "listen", fake_listen)
+	monkeypatch.setattr(cli.asyncio, "run", fake_run)
+
+	cli.main()
+
+	assert seen["cache"] == "memory://"
+	assert seen["receivers"] == (receiver_1, receiver_2)
+	assert seen["listen_args"] == (config, listener, (receiver_1, receiver_2))
+	assert seen["run"] == (fake_coroutine, FakeLoopFactory.make_loop, False)