diff --git a/beacon/light/sync/head_sync_test.go b/beacon/light/sync/head_sync_test.go
index 325a597f7b..0451457f3d 100644
--- a/beacon/light/sync/head_sync_test.go
+++ b/beacon/light/sync/head_sync_test.go
@@ -53,10 +53,12 @@ func TestValidatedHead(t *testing.T) {
 	ts.AddServer(testServer1, 1)
 	ts.ServerEvent(EvNewSignedHead, testServer1, testSHead1)
 	ts.Run(1, nil, nil)
+	// announced head should be queued because of uninitialized chain
 	ht.ExpValidated(t, 1, nil)
 
-	chain.SetNextSyncPeriod(0)
+	chain.SetNextSyncPeriod(0) // initialize chain
 	ts.Run(2, nil, nil)
+	// expect previously queued head to be validated
 	ht.ExpValidated(t, 2, []types.SignedHeader{testSHead1})
 
 	chain.SetNextSyncPeriod(1)
@@ -64,28 +66,34 @@ func TestValidatedHead(t *testing.T) {
 	ts.AddServer(testServer2, 1)
 	ts.ServerEvent(EvNewSignedHead, testServer2, testSHead2)
 	ts.Run(3, nil, nil)
+	// expect both head announcements to be validated instantly
 	ht.ExpValidated(t, 3, []types.SignedHeader{testSHead2, testSHead2})
 
 	ts.ServerEvent(EvNewSignedHead, testServer1, testSHead3)
 	ts.AddServer(testServer3, 1)
 	ts.ServerEvent(EvNewSignedHead, testServer3, testSHead4)
 	ts.Run(4, nil, nil)
+	// future period annonced heads should be queued
 	ht.ExpValidated(t, 4, nil)
 
 	chain.SetNextSyncPeriod(2)
 	ts.Run(5, nil, nil)
+	// testSHead3 can be validated now but not testSHead4
 	ht.ExpValidated(t, 5, []types.SignedHeader{testSHead3})
 
+	// server 3 disconnected without proving period 3, its announced head should be dropped
 	ts.RemoveServer(testServer3)
 	ts.Run(6, nil, nil)
 	ht.ExpValidated(t, 6, nil)
 
 	chain.SetNextSyncPeriod(3)
 	ts.Run(7, nil, nil)
+	// testSHead4 could be validated now but it's not queued by any registered server
 	ht.ExpValidated(t, 7, nil)
 
 	ts.ServerEvent(EvNewSignedHead, testServer2, testSHead4)
 	ts.Run(8, nil, nil)
+	// now testSHead4 should be validated
 	ht.ExpValidated(t, 8, []types.SignedHeader{testSHead4})
 }