From 87e8afc0fd8a0f8dba0fd7ef9dece95bf86e8a33 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Thu, 6 May 2021 16:00:50 +0000
Subject: [PATCH] Avoid crash on degenerate test case

---
 controllers/events/mocks_for_test.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/controllers/events/mocks_for_test.go b/controllers/events/mocks_for_test.go
index 3022cfe..36726fd 100644
--- a/controllers/events/mocks_for_test.go
+++ b/controllers/events/mocks_for_test.go
@@ -137,6 +137,9 @@ func (f *fakeExporter) sort() {
 			topSpan = i
 		}
 	}
+	if topSpan == -1 { // no top span found; can't do DFS
+		return
+	}
 
 	sortedSpans := make([]*tracesdk.SpanSnapshot, 0, len(f.SpanSnapshot))
 	t := dfs{