test(providers): cover the registry and the app's catalogue independence

Registry lookup and its fallback for a stale slug, SomaFM branding and guessed mirrors, provider round-trip in the config, legacy-config migration and BEEFY_*/SOMAFM_* precedence - plus an end-to-end boot against a fake second provider, which is what actually proves the UI no longer knows about SomaFM.

tests/test_providers.py

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+from __future__ import annotations
+
+import html
+import json
+import re
+
+import pytest
+
+from beefy_player import config
+from beefy_player.models import Song, Station
+from beefy_player.providers import PROVIDERS, available_providers, get_provider
+from beefy_player.providers.base import RadioProvider
+from beefy_player.providers.somafm import SomaFMProvider
+
+
+def rendered_text(app) -> str:
+    svg = html.unescape(app.export_screenshot()).replace("\xa0", " ")
+    return re.sub(r"<[^>]+>", " ", svg)
+
+
+def test_registry_lists_somafm_as_the_default() -> None:
+    assert available_providers() == ("somafm",)
+    assert isinstance(get_provider(), SomaFMProvider)
+    assert get_provider("somafm") is get_provider()
+    # a stale slug in the config file must not stop the app from starting
+    assert get_provider("no-such-catalogue") is get_provider()
+
+
+def test_somafm_provider_describes_its_catalogue() -> None:
+    provider = get_provider()
+    assert provider.name == "SomaFM"
+    assert provider.brand == "SOMA FM"
+    assert provider.station_source == "somafm.com/channels.json"
+    assert "somafm.com" in provider.user_agent
+
+    stations = provider.fallback_stations()
+    assert len(stations) > 40
+    station = stations[0]
+    assert station.provider == "somafm"
+    assert station.uid == f"somafm:{station.id}"
+    assert all("somafm.com" in url for url in provider.fallback_urls(station))
+
+
+class FakeProvider(RadioProvider):
+    """A second catalogue, as small as the interface allows."""
+
+    id = "fake"
+    name = "Fake FM"
+    homepage = "fake.test"
+    brand = "FAKE FM"
+    tagline = "not real radio"
+    station_source = "fake.test/stations.json"
+    history_source = "recent.json"
+
+    def __init__(self) -> None:
+        self.station = Station(
+            id="one", title="Fake One", genre="test", provider=self.id
+        )
+
+    async def fetch_stations(self, client):
+        return [self.station]
+
+    def load_cached_stations(self):
+        return [self.station]
+
+    def fallback_stations(self):
+        return [self.station]
+
+    async def fetch_history(self, client, station_id):
+        return [Song(title="Tune", artist="Someone")]
+
+    def load_cached_history(self, station_id):
+        return []
+
+
+@pytest.mark.asyncio
+async def test_app_runs_against_a_different_catalogue(monkeypatch) -> None:
+    """The UI must not know which catalogue it is showing."""
+    from beefy_player.app import BeefyPlayerApp
+
+    fake = FakeProvider()
+    monkeypatch.setitem(PROVIDERS, "fake", fake)
+    app = BeefyPlayerApp(provider="fake", autoplay=False, offline=True, audio=False)
+    assert app.provider is fake
+    async with app.run_test(size=(100, 30)) as pilot:
+        await pilot.pause()
+        assert app.current is not None
+        assert app.current.uid == "fake:one"
+        app.query_one("StagePanel").refresh_stage()
+        await pilot.pause()
+        text = rendered_text(app)
+        assert "FAKE ONE" in text
+        assert "Fake FM" in app.title
+
+
+def test_config_remembers_the_provider() -> None:
+    assert config.Config.load().provider == "somafm"
+    config.Config(provider="fake").save()
+    assert config.Config.load().provider == "fake"
+
+
+def test_legacy_config_is_migrated_once(monkeypatch) -> None:
+    legacy = config.LEGACY_CONFIG_PATH
+    legacy.parent.mkdir(parents=True, exist_ok=True)
+    legacy.write_text(
+        json.dumps({"favorites": ["defcon"], "volume": 33, "last_station": "dronezone"})
+    )
+
+    loaded = config.Config.load()
+    assert loaded.favorites == ["defcon"]
+    assert loaded.volume == 33
+    assert loaded.last_station == "dronezone"
+    assert config.CONFIG_PATH.exists()
+
+    # the new file wins from then on
+    config.Config(volume=11).save()
+    legacy.write_text(json.dumps({"volume": 99}))
+    assert config.Config.load().volume == 11
+
+
+def test_environment_variables_prefer_the_beefy_prefix(monkeypatch) -> None:
+    monkeypatch.setenv("BEEFY_IMAGES", "tgp")
+    monkeypatch.setenv("SOMAFM_IMAGES", "0")
+    assert config.env_var("IMAGES") == "tgp"
+
+    monkeypatch.delenv("BEEFY_IMAGES")
+    assert config.env_var("IMAGES") == "0"  # the old spelling still works
+
+    monkeypatch.delenv("SOMAFM_IMAGES")
+    assert config.env_var("IMAGES") == ""