fix(pre-alpha): preserve injected backtest services

tests/test_backtest_ui.py

@@ -4,7 +4,10 @@ from datetime import date
 
 import pytest
 
+from app.services.backtesting.historical_provider import SyntheticHistoricalProvider
+from app.services.backtesting.service import BacktestService
 from app.services.backtesting.ui_service import BacktestPageService
+from tests.helpers_backtest_sources import StaticBacktestSource
 
 
 def test_backtest_page_service_uses_fixture_window_for_deterministic_run() -> None:
@@ -186,6 +189,23 @@ def test_backtest_preview_validation_requires_supported_fixture_window_even_with
         )
 
 
+def test_backtest_preview_validation_accepts_close_supplied_entry_spot() -> None:
+    service = BacktestPageService()
+
+    entry_spot = service.validate_preview_inputs(
+        symbol="GLD",
+        start_date=date(2024, 1, 2),
+        end_date=date(2024, 1, 8),
+        template_slug="protective-put-atm-12m",
+        underlying_units=1000.0,
+        loan_amount=68000.0,
+        margin_call_ltv=0.75,
+        entry_spot=100.005,
+    )
+
+    assert entry_spot == 100.0
+
+
 def test_backtest_preview_validation_rejects_mismatched_supplied_entry_spot() -> None:
     service = BacktestPageService()
 
@@ -200,3 +220,17 @@ def test_backtest_preview_validation_rejects_mismatched_supplied_entry_spot() ->
             margin_call_ltv=0.75,
             entry_spot=99.0,
         )
+
+
+def test_backtest_page_service_does_not_mutate_injected_backtest_service() -> None:
+    provider = SyntheticHistoricalProvider(
+        source=StaticBacktestSource(),
+        implied_volatility=0.2,
+        risk_free_rate=0.01,
+    )
+    injected_service = BacktestService(provider=provider)
+
+    BacktestPageService(backtest_service=injected_service)
+
+    history = injected_service.provider.load_history("GLD", date(2024, 1, 3), date(2024, 1, 3))
+    assert history[0].close == 123.0