Add configurable data providers and localize frontend UI

backend/tests/test_provider_router.py

@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+"""Tests for provider router fallback behavior."""
+
+from backend.data.provider_router import DataProviderRouter
+from backend.config.data_config import reset_config
+
+
+def test_router_includes_local_csv_fallback(monkeypatch):
+    monkeypatch.delenv("FINNHUB_API_KEY", raising=False)
+    monkeypatch.delenv("FINANCIAL_DATASETS_API_KEY", raising=False)
+    monkeypatch.delenv("FIN_DATA_SOURCE", raising=False)
+    reset_config()
+
+    router = DataProviderRouter()
+
+    assert router.price_sources() == ["local_csv"]
+
+
+def test_router_allows_yfinance_when_enabled(monkeypatch):
+    monkeypatch.setenv("FIN_DATA_SOURCE", "yfinance")
+    monkeypatch.setenv("ENABLED_DATA_SOURCES", "yfinance,local_csv")
+    monkeypatch.delenv("FINNHUB_API_KEY", raising=False)
+    monkeypatch.delenv("FINANCIAL_DATASETS_API_KEY", raising=False)
+    reset_config()
+
+    router = DataProviderRouter()
+
+    assert router.price_sources() == ["yfinance", "local_csv"]
+    assert router.api_sources() == ["yfinance"]