Extract shared build_metric_registry factory (DRY)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/test_question_history.py

@@ -0,0 +1,131 @@
+"""Tests for the cross-run question-history index used by the report page."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from webapp.services.question_history import (
+    build_question_history_index,
+    lookup,
+    normalize_question,
+)
+
+
+def _write_run(
+    run_dir: Path,
+    *,
+    run_id: str,
+    scenario_name: str,
+    finished_at: str,
+    rows: list[tuple[str, float]],
+    metric: str = "faithfulness",
+) -> None:
+    """Create a minimal run directory (metadata.json + scores.csv)."""
+    run_dir.mkdir(parents=True, exist_ok=True)
+    import json
+
+    (run_dir / "metadata.json").write_text(
+        json.dumps(
+            {
+                "run_id": run_id,
+                "scenario_name": scenario_name,
+                "finished_at": finished_at,
+                "valid_samples": len(rows),
+                "invalid_samples": 0,
+            }
+        ),
+        encoding="utf-8",
+    )
+    lines = [f"sample_id,question,{metric}"]
+    for i, (question, score) in enumerate(rows):
+        lines.append(f"s{i},{question},{score}")
+    (run_dir / "scores.csv").write_text("\n".join(lines), encoding="utf-8")
+
+
+# A question unlikely to collide with anything under the real outputs/ tree.
+_Q = "UNIQTESTQ ball tube lifetime evaluation method 9f3a"
+
+
+def test_normalize_question_is_case_and_whitespace_insensitive() -> None:
+    assert normalize_question("  Hello   World ") == normalize_question("hello world")
+
+
+def test_index_matches_question_across_runs_newest_first(tmp_path: Path) -> None:
+    _write_run(
+        tmp_path / "runA",
+        run_id="runA",
+        scenario_name="scnA",
+        finished_at="2026-01-01T00:00:00",
+        rows=[(_Q, 0.40)],
+    )
+    _write_run(
+        tmp_path / "runB",
+        run_id="runB",
+        scenario_name="scnB",
+        finished_at="2026-02-01T00:00:00",
+        rows=[(_Q, 0.80)],
+    )
+
+    index = build_question_history_index(extra_roots=[tmp_path])
+    entries = lookup(index, _Q)
+
+    assert [e["run_id"] for e in entries] == ["runB", "runA"]  # newest first
+    assert entries[0]["metrics"]["faithfulness"] == 0.80
+    assert entries[1]["scenario_name"] == "scnA"
+
+
+def test_index_excludes_current_run(tmp_path: Path) -> None:
+    _write_run(
+        tmp_path / "cur",
+        run_id="cur",
+        scenario_name="scn",
+        finished_at="2026-03-01T00:00:00",
+        rows=[(_Q, 0.50)],
+    )
+    _write_run(
+        tmp_path / "prev",
+        run_id="prev",
+        scenario_name="scn",
+        finished_at="2026-01-01T00:00:00",
+        rows=[(_Q, 0.60)],
+    )
+
+    index = build_question_history_index(exclude_run_id="cur", extra_roots=[tmp_path])
+    entries = lookup(index, _Q)
+
+    assert [e["run_id"] for e in entries] == ["prev"]
+
+
+def test_index_keeps_latest_occurrence_within_a_run(tmp_path: Path) -> None:
+    _write_run(
+        tmp_path / "run1",
+        run_id="run1",
+        scenario_name="scn",
+        finished_at="2026-01-01T00:00:00",
+        rows=[(_Q, 0.30), (_Q, 0.70)],  # same question twice
+    )
+
+    index = build_question_history_index(extra_roots=[tmp_path])
+    entries = lookup(index, _Q)
+
+    assert len(entries) == 1
+    assert entries[0]["metrics"]["faithfulness"] == 0.70  # last occurrence wins
+
+
+def test_lookup_caps_at_limit(tmp_path: Path) -> None:
+    for i in range(7):
+        _write_run(
+            tmp_path / f"r{i}",
+            run_id=f"r{i}",
+            scenario_name="scn",
+            finished_at=f"2026-01-0{i + 1}T00:00:00",
+            rows=[(_Q, 0.1 * i)],
+        )
+
+    index = build_question_history_index(extra_roots=[tmp_path])
+    assert len(lookup(index, _Q, limit=3)) == 3
+
+
+def test_lookup_unknown_question_returns_empty(tmp_path: Path) -> None:
+    index = build_question_history_index(extra_roots=[tmp_path])
+    assert lookup(index, "NO SUCH QUESTION zzz 0000") == []