fix(pre-alpha): preserve injected backtest services

app/services/backtesting/ui_service.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 from datetime import date
+from math import isclose
 
 from app.domain.backtesting_math import materialize_backtest_portfolio_state
 from app.models.backtest import (
@@ -10,7 +11,7 @@ from app.models.backtest import (
     ProviderRef,
     TemplateRef,
 )
-from app.services.backtesting.historical_provider import DailyClosePoint
+from app.services.backtesting.historical_provider import DailyClosePoint, SyntheticHistoricalProvider
 from app.services.backtesting.service import BacktestService
 from app.services.strategy_templates import StrategyTemplateService
 
@@ -64,12 +65,19 @@ class BacktestPageService:
         template_service: StrategyTemplateService | None = None,
     ) -> None:
         self.template_service = template_service or StrategyTemplateService()
-        self.backtest_service = backtest_service or BacktestService(
+        base_service = backtest_service or BacktestService(
             template_service=self.template_service,
             provider=None,
         )
-        provider = self.backtest_service.provider
-        provider.source = DeterministicBacktestFixtureSource()
+        fixture_provider = SyntheticHistoricalProvider(
+            source=DeterministicBacktestFixtureSource(),
+            implied_volatility=base_service.provider.implied_volatility,
+            risk_free_rate=base_service.provider.risk_free_rate,
+        )
+        self.backtest_service = BacktestService(
+            provider=fixture_provider,
+            template_service=self.template_service,
+        )
 
     def template_options(self, symbol: str = "GLD") -> list[dict[str, str | int]]:
         return [
@@ -122,7 +130,12 @@ class BacktestPageService:
 
         self.template_service.get_template(template_slug)
         derived_entry_spot = self.derive_entry_spot(normalized_symbol, start_date, end_date)
-        if entry_spot is not None and entry_spot != derived_entry_spot:
+        if entry_spot is not None and not isclose(
+            entry_spot,
+            derived_entry_spot,
+            rel_tol=BacktestService.ENTRY_SPOT_REL_TOLERANCE,
+            abs_tol=BacktestService.ENTRY_SPOT_ABS_TOLERANCE,
+        ):
             raise ValueError(
                 f"Supplied entry spot ${entry_spot:,.2f} does not match derived historical entry spot ${derived_entry_spot:,.2f}"
             )