Refactor: consolidate duplicated _elapsed_ms and remove one-liner wrapper

src/nexa_backtest/engines/backtest.py

@@ -840,7 +840,7 @@ def run(self) -> BacktestResult:
             registry.register(provider)
 
         # Determine the zone (first product wins)
-        zone = self._parse_zone()
+        zone = _parse_zone(self._products[0])
 
         all_fills: list[Fill] = []
         equity_snapshots: list[EquitySnapshot] = []
@@ -1315,10 +1315,6 @@ def _auction_time(delivery_date: date) -> datetime:
         delivery_dt = datetime.combine(delivery_date, time(0, 0), tzinfo=UTC)
         return delivery_dt + _AUCTION_OFFSET
 
-    def _parse_zone(self) -> str:
-        """Extract zone from the first product spec."""
-        return _parse_zone(self._products[0])
-
 
 def _mtu_to_product_id(mtu_start: datetime, zone: str) -> str:
     """Convert an MTU start time to a Nord Pool IDC product ID.

src/nexa_backtest/validation/_utils.py

@@ -0,0 +1,10 @@
+"""Shared utilities for validation check modules."""
+
+from __future__ import annotations
+
+import time
+
+
+def _elapsed_ms(start: float) -> int:
+    """Return milliseconds elapsed since ``start`` (from :func:`time.monotonic`)."""
+    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/feature_check.py

@@ -13,6 +13,7 @@
 from pathlib import Path
 
 from nexa_backtest.exchanges.base import ExchangeCapabilities
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # Map exchange name → capabilities factory.
@@ -229,7 +230,3 @@ def _extract_numeric(node: ast.expr) -> float | int | None:
     ):
         return -node.operand.value
     return None
-
-
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/interface_check.py

@@ -11,6 +11,7 @@
 import time
 from pathlib import Path
 
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # Expected hook signatures for SimpleAlgo methods.
@@ -309,7 +310,3 @@ def _check_multiple_definitions(
             f"{filename}: Multiple algo definitions found: {', '.join(names)}. "
             "Place each algo in its own file. Ambiguous file cannot be loaded."
         )
-
-
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/lookahead_check.py

@@ -12,6 +12,7 @@
 import time
 from pathlib import Path
 
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # Large lookback threshold for get_signal_history() in number of MTUs.
@@ -222,7 +223,3 @@ def _check_sort_iloc(
                     "rows that are chronologically in the future after sorting. "
                     "Verify this does not introduce look-ahead bias."
                 )
-
-
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/mypy_check.py

@@ -12,6 +12,7 @@
 import time
 from pathlib import Path
 
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # mypy output line pattern: filename:line: severity: message  [error-code]
@@ -109,7 +110,3 @@ def run(self, algo_path: str) -> StepResult:
             messages=messages,
             duration_ms=duration,
         )
-
-
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/resource_check.py

@@ -10,6 +10,7 @@
 import time
 from pathlib import Path
 
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # Methods/attributes that indicate time.sleep or asyncio.sleep.
@@ -338,7 +339,3 @@ def _check_mutable_globals(
                 "({}) may leak state between backtest runs. "
                 "Move state into the algo class or function.".format(type(val).__name__.lower())
             )
-
-
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)

src/nexa_backtest/validation/ruff_check.py

@@ -12,6 +12,7 @@
 import time
 from pathlib import Path
 
+from nexa_backtest.validation._utils import _elapsed_ms
 from nexa_backtest.validation.runner import StepResult
 
 # Ruff rule codes that indicate hard errors (not merely style issues).
@@ -148,10 +149,6 @@ def run(self, algo_path: str) -> StepResult:
         )
 
 
-def _elapsed_ms(start: float) -> int:
-    return int((time.monotonic() - start) * 1000)
-
-
 def _build_config_args() -> list[str]:
     """Return CLI args that apply the bundled nexa ruff config.