Isolate legacy range-expansion factor

tests/unit/test_backtest_service.py

@@ -763,6 +763,8 @@ def test_sr_research_variant_is_explicit_and_validated(monkeypatch):
         "production_control",
         "legacy_range_grid_touch",
         "legacy_range_grid_neutral",
+        "production_range504",
+        "rewrite_range504_legacy_primary",
     ):
         monkeypatch.setenv("BACKTEST_SR_VARIANT", variant)
         assert bt._sr_research_variant() == variant
@@ -771,6 +773,29 @@ def test_sr_research_variant_is_explicit_and_validated(monkeypatch):
         bt._sr_research_variant()
 
 
+def test_range_factor_detector_mapping_is_explicit():
+    assert bt._sr_detector_variant("production_range504") == "production_control"
+    assert bt._sr_detector_variant("rewrite_range504_legacy_primary") == "rewrite"
+    assert bt._sr_detector_variant("soft_zones_legacy_primary") == "soft_zones"
+
+
+def test_range_504_log_uses_only_the_bounded_window():
+    highs = [1_000.0, *([100.0] * bt.RANGE_FACTOR_LOOKBACK)]
+    lows = [10.0, *([50.0] * bt.RANGE_FACTOR_LOOKBACK)]
+    assert bt._range_504_log(highs, lows) == pytest.approx(math.log(2.0))
+
+
+def test_range_factor_gate_is_research_arm_only():
+    below = bt.RANGE_FACTOR_MIN_LOG - 0.01
+    assert not bt._range_factor_allows("production_range504", below)
+    assert not bt._range_factor_allows("rewrite_range504_legacy_primary", below)
+    assert bt._range_factor_allows(
+        "production_range504",
+        bt.RANGE_FACTOR_MIN_LOG,
+    )
+    assert bt._range_factor_allows("production_control", below)
+
+
 @pytest.mark.parametrize(
     ("variant", "neutral_strength"),
     [
@@ -863,6 +888,9 @@ def test_replay_ticker_candidates_carry_gate_fields():
     for c in cands:
         assert c.get("action") is not None
         assert "risk_level" in c
+        assert c["range_504_log"] >= 0.0
+        assert c["range_504_ratio"] >= 1.0
+        assert isinstance(c["range_factor_pass"], bool)
 
 
 async def _seed_oscillating_ticker(session, symbol: str, n: int = 160) -> None: