feat(detection-core): measured per-class budget replacing the static 120s gate

tests/test_core_budget.py

@@ -0,0 +1,60 @@
+"""Measured-budget contract tests for detection-core task 2 (Req 4, 12)."""
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
+
+from openultrasast.core.budget import (  # noqa: E402
+    Budget,
+    BudgetGateFailure,
+    Complexity,
+    check_budget,
+    derive_budget,
+)
+
+SAMPLES = tuple((Complexity(regions=1 + i % 3, calls=10 * i, changed_bytes=100 * i), float(1 + i)) for i in range(20))
+
+
+def test_derive_budget_publishes_derivation_metadata() -> None:
+    budget = derive_budget(SAMPLES, workload_class="dev-pool", percentile=0.95, hardware="ci-runner-4cpu")
+    assert isinstance(budget, Budget)
+    assert budget.workload_class == "dev-pool"
+    assert budget.n == 20
+    assert budget.percentile == 0.95
+    assert budget.hardware == "ci-runner-4cpu"
+    assert budget.seconds == 19.05  # linear-interpolated p95 of samples 1..20
+
+
+def test_derive_budget_is_deterministic() -> None:
+    first = derive_budget(SAMPLES, workload_class="pilot", percentile=0.9, hardware="h")
+    second = derive_budget(SAMPLES, workload_class="pilot", percentile=0.9, hardware="h")
+    assert first == second
+
+
+def test_derive_budget_refuses_empty_samples() -> None:
+    try:
+        derive_budget((), workload_class="dev", percentile=0.95, hardware="h")
+        raise AssertionError("empty sample set must be refused")
+    except ValueError:
+        pass
+
+
+def test_budget_is_configurable_per_class_not_a_constant() -> None:
+    dev = derive_budget(SAMPLES, workload_class="dev-pool", percentile=0.95, hardware="h")
+    pilot = derive_budget(tuple((c, s / 10) for c, s in SAMPLES), workload_class="pilot", percentile=0.95, hardware="h")
+    assert dev.seconds != pilot.seconds
+    assert dev.workload_class != pilot.workload_class
+
+
+def test_budget_gate_names_change_elapsed_and_derivation() -> None:
+    budget = derive_budget(SAMPLES, workload_class="dev-pool", percentile=0.95, hardware="ci-runner-4cpu")
+    check_budget("case-1", 5.0, budget)
+    try:
+        check_budget("case-2", 999.0, budget)
+        raise AssertionError("over-budget change must fail the gate")
+    except BudgetGateFailure as error:
+        message = str(error)
+        assert "case-2" in message
+        assert "999" in message
+        assert "dev-pool" in message and "ci-runner-4cpu" in message and "n=20" in message