diff --git a/hoppys-adventure-arcade/tests/platformer_stage_clear.gd b/hoppys-adventure-arcade/tests/platformer_stage_clear.gd
index ac182c09..7e03dc5b 100644
--- a/hoppys-adventure-arcade/tests/platformer_stage_clear.gd
+++ b/hoppys-adventure-arcade/tests/platformer_stage_clear.gd
@@ -27,18 +27,26 @@ func run() -> void:
 	var stream := load(STINGER) as AudioStreamOggVorbis
 	check(stream != null and not stream.loop and stream.get_length() > 2.0 and stream.get_length() < 6.0,
 		"The stage-clear stinger is a short one-shot")
+	if stream == null:
+		await finish()
+		return
 	for route in LEVELS:
 		await open_level(route)
 		check(game.stage_clear.stream == stream and not game.stage_clear.playing, route + ": the stinger waits for the finish")
 		game._finish(true)
-		await create_timer(0.5, true, false, true).timeout
+		# _finish(true) starts the stinger synchronously, so this window counts from "stopped".
+		var early := await watch(game.stage_clear, 0.5, true)
 		check(paused and game.stage_clear.playing and game.stage_clear.bus == &"Music",
 			route + ": MERGE SUCCESSFUL plays the stinger on the Music bus while the results pause the tree")
 		check(game.music.process_mode != Node.PROCESS_MODE_ALWAYS and game.music.can_process() == false,
 			route + ": the level music stays paused under the stinger")
+		var rest := await watch(game.stage_clear, stream.get_length())
+		check(early.starts + rest.starts == 1 and not game.stage_clear.playing,
+			route + ": the stage-clear stinger starts once and stops after one playback (%d starts)" % (early.starts + rest.starts))
 		var leave := game.find_children("*", "Button", true, false).filter(func(b: Button) -> bool: return b.text == "Return to Platformer Menu")
 		check(not leave.is_empty(), route + ": the results offer a way out")
 		if not leave.is_empty():
+			game.stage_clear.play()
 			(leave[0] as Button).pressed.emit()
 			check(not game.stage_clear.playing, route + ": leaving the results stops the stinger before the level music resumes")
 			await create_timer(0.6, true, false, true).timeout
@@ -46,10 +54,35 @@ func run() -> void:
 		await open_level(route)
 		game.player.position.y = 900
 		game.player._physics_process(0.0)
-		await create_timer(0.5, true, false, true).timeout
-		check(not game.stage_clear.playing, route + ": a knockout does not play the stage-clear stinger")
+		check(game.finished and not game.won_run, route + ": the fall enters knockout handling")
+		# The knockout cutaway runs for 3.5 s before the shared results open; watch every frame of both.
+		var knockout := await watch(game.stage_clear, 3.6)
+		check(not knockout.ever_playing and not game.stage_clear.playing,
+			route + ": a knockout and its results never play the stage-clear stinger")
 		paused = false
+	await finish()
+
+## Samples the player every frame, paused or not: how many times playback started (from stopped,
+## or by jumping back to the start) and whether it played at all.
+func watch(player: AudioStreamPlayer, seconds: float, from_stopped := false) -> Dictionary:
+	var deadline := Time.get_ticks_msec() + int(seconds * 1000.0)
+	var was_playing := player.playing and not from_stopped
+	var last_position := player.get_playback_position() if was_playing else 0.0
+	var result := {"starts": 0, "ever_playing": player.playing}
+	while Time.get_ticks_msec() < deadline:
+		await process_frame
+		var playing := player.playing
+		var position := player.get_playback_position() if playing else 0.0
+		if playing and (not was_playing or position + 0.05 < last_position):
+			result.starts += 1
+		result.ever_playing = result.ever_playing or playing
+		was_playing = playing
+		last_position = position
+	return result
+
+func finish() -> void:
 	print("PLATFORMER STAGE CLEAR: %s (%d failures)" % ["PASS" if failures == 0 else "FAIL", failures])
+	paused = false
 	change_scene_to_file("res://scenes/main_menu/main_menu.tscn")
 	await process_frame
 	await root.get_node("AudioService").settle()