test(bench): cover MLX exact recall experiment contracts

tests/test_apple_uma_mlx_exact_recall.py

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+"""Tests for the optional Apple UMA MLX exact recall experiment."""
+
+from __future__ import annotations
+
+import socket
+from unittest import mock
+
+import numpy as np
+
+from benchmarks.apple_uma_mlx_exact_recall import (
+    BENCHMARK_NAME,
+    _parity_report,
+    _stable_top_k_from_scores,
+    run_mlx_exact_recall_experiment,
+)
+
+
+def test_mlx_unavailable_skips_with_explicit_reason() -> None:
+    report = run_mlx_exact_recall_experiment(
+        warmup=1,
+        measured=1,
+        mlx_status={"import_succeeded": False, "reason": "No module named 'mlx'"},
+    )
+
+    assert report["benchmark_name"] == BENCHMARK_NAME
+    assert report["track"] == "mlx_exact_cga_recall"
+    assert report["skipped"] is True
+    assert "MLX unavailable" in report["reason"]
+    assert report["benchmark_only"] is True
+    assert report["serving_authorized"] is False
+    assert report["semantic_backend"] == "python/rust canonical exact recall"
+    assert any("No ANN" in item for item in report["non_claims"])
+    assert any("No serving" in item for item in report["non_claims"])
+
+
+def test_stable_top_k_orders_by_score_then_index() -> None:
+    scores = np.array([0.5, 2.0, 2.0, -1.0, 1.5], dtype=np.float32)
+
+    assert _stable_top_k_from_scores(scores, 3) == [
+        (1, float(scores[1])),
+        (2, float(scores[2])),
+        (4, float(scores[4])),
+    ]
+
+
+def test_parity_report_requires_indices_and_scores_close() -> None:
+    canonical = [(2, 1.25), (5, 0.75)]
+    candidate = [(2, 1.25001), (5, 0.75001)]
+
+    report = _parity_report(canonical=canonical, candidate=candidate)
+
+    assert report["top_k_indices_match"] is True
+    assert report["scores_close"] is True
+    assert report["parity_pass"] is True
+
+
+def test_parity_report_rejects_index_mismatch() -> None:
+    canonical = [(2, 1.25), (5, 0.75)]
+    candidate = [(5, 0.75), (2, 1.25)]
+
+    report = _parity_report(canonical=canonical, candidate=candidate)
+
+    assert report["top_k_indices_match"] is False
+    assert report["parity_pass"] is False
+
+
+def test_experiment_makes_no_network_calls(monkeypatch) -> None:
+    def _blocked(*_a: object, **_k: object) -> None:
+        raise AssertionError("network access attempted during MLX experiment")
+
+    monkeypatch.setattr(socket.socket, "connect", _blocked)
+    run_mlx_exact_recall_experiment(
+        warmup=1,
+        measured=1,
+        mlx_status={"import_succeeded": False, "reason": "No module named 'mlx'"},
+    )
+
+
+def test_mlx_score_vector_is_not_called_when_mlx_unavailable() -> None:
+    with mock.patch(
+        "benchmarks.apple_uma_mlx_exact_recall.mlx_exact_score_vector",
+        side_effect=AssertionError("MLX score path should not run when unavailable"),
+    ):
+        report = run_mlx_exact_recall_experiment(
+            warmup=1,
+            measured=1,
+            mlx_status={"import_succeeded": False, "reason": "No module named 'mlx'"},
+        )
+    assert report["skipped"] is True