diff --git a/android/arch_test.go b/android/arch_test.go
index 46c018a..e445ec6 100644
--- a/android/arch_test.go
+++ b/android/arch_test.go
@@ -584,6 +584,8 @@
 
 func (testArchPropertiesModule) GenerateAndroidBuildActions(ctx ModuleContext) {}
 
+// Module property "a" does not have "variant_prepend" tag.
+// Expected variant property orders are based on this fact.
 func TestArchProperties(t *testing.T) {
 	bp := `
 		module {