From d3632f3a4325d7916c0bdef276a1c24160e4622f Mon Sep 17 00:00:00 2001
From: Ali Kamil <alikamil@gmail.com>
Date: Tue, 21 Jul 2026 13:07:44 -0500
Subject: [PATCH] test: structural O(n) detect_stops test replacing the deleted
 flaky timing one
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The flaky wall-clock test_stop_detection_quadratic_blowup.py (repeatedly a
false-positive across cycles) was removed. Replace its intent with a structural,
op-count assertion: a 40k-sample real dwell (the original "quadratic blowup"
case) is grown once and accepted, so the scan does ~O(N) work — proven by a
tight linear max_scan_work=4*N budget that an O(N^2) recompute would blow past.
No timing threshold, so no flakiness.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 .../test_detect_stops_scan_work_dos.py        | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tests/adversary/test_detect_stops_scan_work_dos.py b/tests/adversary/test_detect_stops_scan_work_dos.py
index f396b74..20452ae 100644
--- a/tests/adversary/test_detect_stops_scan_work_dos.py
+++ b/tests/adversary/test_detect_stops_scan_work_dos.py
@@ -52,6 +52,28 @@ def test_scan_work_budget_raises_on_a_giant_rejected_cluster():
         detect_stops(pts, radius_m=50.0, min_duration_s=300.0, max_scan_work=200_000)
 
 
+def test_one_long_accepted_dwell_scans_in_linear_work():
+    # Structural (op-count, not wall-clock) replacement for the removed flaky
+    # timing test: a real N-sample dwell — the original "quadratic blowup" case —
+    # is grown once, accepted as a stop, and the scan jumps past it, so the total
+    # work is ~O(N). A tight linear budget (4*N) proves it: an O(N^2) recompute
+    # (the pre-incremental-bound behaviour) would blow past it long before the end.
+    n = 40_000
+    base = datetime(2024, 1, 1, tzinfo=timezone.utc)
+    # A dense dwell: many samples jittering within a few metres of one spot.
+    pts = [
+        TrackSample(
+            lat=40.0 + ((i % 5) - 2) * 1e-6,  # ~±0.2 m of jitter
+            lon=-100.0 + ((i % 3) - 1) * 1e-6,
+            ts_utc=base + timedelta(seconds=i),
+        )
+        for i in range(n)
+    ]
+    stops = detect_stops(pts, radius_m=50.0, min_duration_s=300.0, max_scan_work=4 * n)
+    assert len(stops) == 1, "a single long dwell should be one stop"
+    assert stops[0].sample_count == n, "the whole dwell should be one accepted cluster"
+
+
 def test_uncapped_default_is_unchanged_for_a_normal_track():
     # A real drive → dwell → drive with the default (no budget) still finds the
     # one stop; the budget only applies when a caller passes max_scan_work.