diff --git a/app/src/test/java/com/hawhamburg/micr0bu/EventDetectorTest.kt b/app/src/test/java/com/hawhamburg/micr0bu/EventDetectorTest.kt
index d6456f4..87b5f40 100644
--- a/app/src/test/java/com/hawhamburg/micr0bu/EventDetectorTest.kt
+++ b/app/src/test/java/com/hawhamburg/micr0bu/EventDetectorTest.kt
@@ -116,12 +116,17 @@ class EventDetectorTest {
     // ─── Hard brake ───────────────────────────────────────────────────────────
 
     @Test fun `hard brake triggers BRAKING event`() = runCollecting { events ->
-        // Phase 1: fill window at 10 m/s with constant accel (no std dev → no braking)
-        repeat(config.windowSize) { i ->
-            detector.processSample(1.0, 0.05, 10.0, 0.0, 53.5, 10.0, i * 20L)
-        }
-        // Phase 2: GPS drops to 4 m/s (drop = 6 m/s > 0.5 threshold).
-        // Alternate hi/lo accel to exceed the std-dev threshold.
+        // Phase 1: cruising at 10 m/s with the accelerometer variability a moving bike actually
+        // has. This matters: [EventDetector] requires the speed drop and the accel std dev to be
+        // true on the SAME frame, and the std dev is a rolling window. Filling phase 1 with a
+        // constant accel drives that window to zero, so on the one frame where the speed drop
+        // exists the std dev is still ~0.75 and braking can never start - by the time the window
+        // has recovered, prevSpeedMps has caught up and the drop is gone.
+        //
+        // Constant accel right up to the instant of a brake is also not physical. The IMU is
+        // sampled continuously while GPS speed lags, so the shaking precedes the reported drop.
+        alternatingAccelFrames(n = config.windowSize, speedMps = 10.0, timeOffset = 0)
+        // Phase 2: GPS reports 4 m/s (drop = 6 m/s > 0.5 threshold).
         alternatingAccelFrames(
             n          = config.brakingSustainedFrames + 5,
             speedMps   = 4.0,
@@ -132,9 +137,8 @@ class EventDetectorTest {
     }
 
     @Test fun `hard brake with large speed drop has HIGH confidence`() = runCollecting { events ->
-        repeat(config.windowSize) { i ->
-            detector.processSample(1.0, 0.05, 10.0, 0.0, 53.5, 10.0, i * 20L)
-        }
+        // Variability established before the drop - see the note in the test above.
+        alternatingAccelFrames(n = config.windowSize, speedMps = 10.0, timeOffset = 0)
         // Drop of 8 m/s > brakingHighConfidenceRate (1.5)
         alternatingAccelFrames(
             n          = config.brakingSustainedFrames + 5,
@@ -153,9 +157,8 @@ class EventDetectorTest {
     }
 
     @Test fun `moderate speed drop has MEDIUM confidence`() = runCollecting { events ->
-        repeat(config.windowSize) { i ->
-            detector.processSample(1.0, 0.05, 3.0, 0.0, 53.5, 10.0, i * 20L)
-        }
+        // Variability established before the drop - see `hard brake triggers BRAKING event`.
+        alternatingAccelFrames(n = config.windowSize, speedMps = 3.0, timeOffset = 0)
         // Drop of 0.8 m/s — above speed-drop threshold (0.5) but below high-conf rate (1.5)
         alternatingAccelFrames(
             n          = config.brakingSustainedFrames + 5,
@@ -294,8 +297,15 @@ class EventDetectorTest {
         repeat(5) {
             detector.processSample(0.5, 0.1, 5.0, 2.0, 53.5, 10.0, t++ * 20L)
         }
-        // Second stop episode
-        repeat(stopFrames) {
+        // Second stop episode. Deliberately longer than the first: stopping also requires the
+        // accel std dev to be BELOW a threshold, and the rolling window still holds the five
+        // moving samples above. It takes 8 further frames for those to drain out far enough for
+        // the std dev to fall under 0.15, and only then does the counter start. The first episode
+        // needs no such allowance because the window begins empty.
+        //
+        // stoppingFrames + 5 was not enough - the second episode reached 17 of the 21 frames it
+        // needs and silently emitted nothing, which is what made this test fail.
+        repeat(config.stoppingFrames + 10) {
             detector.processSample(0.02, 0.01, 0.1, 0.0, 53.5, 10.0, t++ * 20L)
         }