refactor(BT-001C): share historical fixture provider

tests/test_backtest_ui.py

@@ -282,3 +282,39 @@ def test_backtest_page_service_uses_injected_provider_identity_in_provider_ref()
 
     assert result.scenario.provider_ref.provider_id == "custom_v1"
     assert result.scenario.provider_ref.pricing_mode == "custom_mode"
+
+
+def test_backtest_page_service_preserves_injected_provider_behavior_beyond_history_loading() -> None:
+    class CustomProvider(SyntheticHistoricalProvider):
+        provider_id = "custom_v2"
+        pricing_mode = "custom_mode"
+
+        def price_option_by_type(self, **kwargs: object):
+            quote = super().price_option_by_type(**kwargs)
+            return quote.__class__(
+                position_id=quote.position_id,
+                leg_id=quote.leg_id,
+                spot=quote.spot,
+                strike=quote.strike,
+                expiry=quote.expiry,
+                quantity=quote.quantity,
+                mark=42.0,
+            )
+
+    provider = CustomProvider(source=StaticBacktestSource(), implied_volatility=0.2, risk_free_rate=0.01)
+    injected_service = BacktestService(provider=provider)
+    page_service = BacktestPageService(backtest_service=injected_service)
+
+    result = page_service.run_read_only_scenario(
+        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,
+    )
+
+    template_result = result.run_result.template_results[0]
+    assert template_result.daily_path[0].option_market_value == 42000.0
+    assert template_result.summary_metrics.total_hedge_cost == 42000.0

tests/test_backtesting_fixture_source.py

@@ -0,0 +1,74 @@
+from __future__ import annotations
+
+from datetime import date
+
+import pytest
+
+from app.services.backtesting.fixture_source import (
+    SEEDED_GLD_2024_FIXTURE_HISTORY,
+    SharedHistoricalFixtureSource,
+    WindowPolicy,
+)
+from app.services.backtesting.ui_service import BacktestPageService
+from app.services.event_comparison_ui import EventComparisonPageService
+
+
+def test_shared_fixture_source_exact_window_requires_seeded_bounds() -> None:
+    source = SharedHistoricalFixtureSource(
+        feature_label="BT-001A",
+        supported_symbol="GLD",
+        history=SEEDED_GLD_2024_FIXTURE_HISTORY,
+        window_policy=WindowPolicy.EXACT,
+    )
+
+    rows = source.load_daily_closes("GLD", date(2024, 1, 2), date(2024, 1, 8))
+
+    assert [row.date.isoformat() for row in rows] == [
+        "2024-01-02",
+        "2024-01-03",
+        "2024-01-04",
+        "2024-01-05",
+        "2024-01-08",
+    ]
+
+    with pytest.raises(ValueError, match="seeded 2024-01-02 through 2024-01-08 window"):
+        source.load_daily_closes("GLD", date(2024, 1, 3), date(2024, 1, 8))
+
+
+def test_shared_fixture_source_bounded_window_allows_subranges_but_fails_closed_outside_seeded_bounds() -> None:
+    source = SharedHistoricalFixtureSource(
+        feature_label="BT-003A",
+        supported_symbol="GLD",
+        history=SEEDED_GLD_2024_FIXTURE_HISTORY,
+        window_policy=WindowPolicy.BOUNDED,
+    )
+
+    rows = source.load_daily_closes("GLD", date(2024, 1, 3), date(2024, 1, 5))
+
+    assert [row.date.isoformat() for row in rows] == ["2024-01-03", "2024-01-04", "2024-01-05"]
+
+    with pytest.raises(ValueError, match="seeded 2024-01-02 through 2024-01-08 window"):
+        source.load_daily_closes("GLD", date(2024, 1, 1), date(2024, 1, 8))
+
+    with pytest.raises(ValueError, match="start_date must be on or before end_date"):
+        source.load_daily_closes("GLD", date(2024, 1, 5), date(2024, 1, 3))
+
+
+def test_backtest_page_service_uses_shared_exact_fixture_source() -> None:
+    service = BacktestPageService()
+
+    source = service.backtest_service.provider.source
+
+    assert isinstance(source, SharedHistoricalFixtureSource)
+    assert source.feature_label == "BT-001A"
+    assert source.window_policy is WindowPolicy.EXACT
+
+
+def test_event_comparison_page_service_uses_shared_bounded_fixture_source() -> None:
+    service = EventComparisonPageService()
+
+    source = service.comparison_service.provider.source
+
+    assert isinstance(source, SharedHistoricalFixtureSource)
+    assert source.feature_label == "BT-003A"
+    assert source.window_policy is WindowPolicy.BOUNDED