feat(s51): fail-fast self-contained routing config loader

Gate: pytest tests/test_hitl.py -k routing_config → 6 passed.

tests/test_hitl.py

@@ -15,6 +15,9 @@ from __future__ import annotations
 import json
 from pathlib import Path
 
+import pytest
+from pydantic import ValidationError
+
 from portfolio_optimiser.ir import AffectedItem, SavingsProposal
 from portfolio_optimiser.outbox import write_outbox
 from portfolio_optimiser.provenance import Citation, ProvenanceStamp
@@ -138,3 +141,75 @@ def test_hitl_registered_maf_free() -> None:
     from tests.test_okf import _MAF_FREE_MODULES
 
     assert "hitl.py" in _MAF_FREE_MODULES
+
+
+# --- load_routing_config() fail-fast ---------------------------------------------------------------
+
+
+def _write_config(tmp_path: Path, data: dict) -> Path:
+    p = tmp_path / "routing-config.json"
+    p.write_text(json.dumps(data), encoding="utf-8")
+    return p
+
+
+_WELLFORMED_CONFIG = {
+    "_note": "ignored underscore key",
+    "entries": [
+        {
+            "id": "energi",
+            "allowed_measure_types": ["scope_reduction"],
+            "allowed_code_prefixes": ["05"],
+            "expert": "Ola Energi",
+        },
+        {"id": "vei", "allowed_code_prefixes": ["03"], "expert": "Kari Vei"},
+    ],
+}
+
+
+def test_routing_config_loads_wellformed(tmp_path: Path) -> None:
+    """A well-formed config loads: entries + experts present, ``_``-prefixed top-level keys stripped."""
+    config = hitl.load_routing_config(_write_config(tmp_path, _WELLFORMED_CONFIG))
+    assert [e.id for e in config.entries] == ["energi", "vei"]
+    assert {e.expert for e in config.entries} == {"Ola Energi", "Kari Vei"}
+    assert config.entries[1].allowed_measure_types == frozenset()  # empty default = "any measure"
+
+
+def test_routing_config_missing_expert_raises(tmp_path: Path) -> None:
+    """An entry missing the required ``expert`` field fails validation."""
+    bad = {"entries": [{"id": "energi", "allowed_code_prefixes": ["05"]}]}
+    with pytest.raises(ValidationError):
+        hitl.load_routing_config(_write_config(tmp_path, bad))
+
+
+def test_routing_config_duplicate_id_raises(tmp_path: Path) -> None:
+    """Two entries with the same ``id`` raise (ValueError via the after-validator)."""
+    dup = {
+        "entries": [
+            {"id": "energi", "expert": "A"},
+            {"id": "energi", "expert": "B"},
+        ]
+    }
+    with pytest.raises(ValueError):
+        hitl.load_routing_config(_write_config(tmp_path, dup))
+
+
+def test_routing_config_wrong_types_raise(tmp_path: Path) -> None:
+    """A non-list ``entries`` (wrong shape) raises."""
+    with pytest.raises(ValidationError):
+        hitl.load_routing_config(_write_config(tmp_path, {"entries": {"id": "x", "expert": "y"}}))
+
+
+def test_routing_config_missing_file_raises(tmp_path: Path) -> None:
+    """A missing config file fails fast with ``FileNotFoundError`` (mirrors ``load_pricing``)."""
+    with pytest.raises(FileNotFoundError):
+        hitl.load_routing_config(tmp_path / "no-such-routing-config.json")
+
+
+def test_routing_config_valid_variant_loads(tmp_path: Path) -> None:
+    """Control: a minimal valid config (single entry, no code/measure constraints) loads — proving
+    the raises above fire only on the bad case, not always."""
+    config = hitl.load_routing_config(
+        _write_config(tmp_path, {"entries": [{"id": "generalist", "expert": "Per"}]})
+    )
+    assert config.entries[0].expert == "Per"
+    assert config.entries[0].allowed_code_prefixes == frozenset()