diff --git a/test/cmp.go b/test/cmp.go
index a9d0375..a56ca6e 100644
--- a/test/cmp.go
+++ b/test/cmp.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test equality and inequality operations.
+
 package main
 
 import "unsafe"