2 files changed, 45 insertions, 0 deletions
diff --git a/core/test/app.go b/core/test/app.go
index ddce31a..e26c20c 100644
--- a/core/test/app.go
+++ b/core/test/app.go
@@ -50,6 +50,10 @@ var (
 	// and delivered are different.
 	ErrMismatchTotalOrderingAndDelivered = fmt.Errorf(
 		"mismatch total ordering and delivered sequence")
+	// ErrNotaryAckUnknownBlock means the notary ack is acking on the unknown
+	// block.
+	ErrNotaryAckUnknownBlock = fmt.Errorf(
+		"notary ack on unknown block")
 )
 
 // AppAckedRecord caches information when this application received
@@ -83,6 +87,8 @@ type App struct {
 	Delivered          map[common.Hash]*AppDeliveredRecord
 	DeliverSequence    common.Hashes
 	deliveredLock      sync.RWMutex
+	NotaryAckSequence  []*types.NotaryAck
+	notaryAckLock      sync.RWMutex
 }
 
 // NewApp constructs a TestApp instance.
@@ -137,6 +143,10 @@ func (app *App) DeliverBlock(blockHash common.Hash, timestamp time.Time) {
 
 // NotaryAckDeliver implements Application interface.
 func (app *App) NotaryAckDeliver(notaryAck *types.NotaryAck) {
+	app.notaryAckLock.Lock()
+	defer app.notaryAckLock.Unlock()
+
+	app.NotaryAckSequence = append(app.NotaryAckSequence, notaryAck)
 }
 
 // Compare performs these checks against another App instance
@@ -224,6 +234,15 @@ Loop:
 		// by total ordering.
 		return ErrMismatchTotalOrderingAndDelivered
 	}
+
+	// Make sure that notaryAck is acking the correct block.
+	app.notaryAckLock.RLock()
+	defer app.notaryAckLock.RUnlock()
+	for _, notaryAck := range app.NotaryAckSequence {
+		if _, exists := app.Delivered[notaryAck.NotaryBlockHash]; !exists {
+			return ErrNotaryAckUnknownBlock
+		}
+	}
 	return nil
 }
 
diff --git a/core/test/app_test.go b/core/test/app_test.go
index f4c4a74..6966de5 100644
--- a/core/test/app_test.go
+++ b/core/test/app_test.go
@@ -1,3 +1,20 @@
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
 package test
 
 import (
@@ -5,6 +22,7 @@ import (
 	"time"
 
 	"github.com/dexon-foundation/dexon-consensus-core/common"
+	"github.com/dexon-foundation/dexon-consensus-core/core/types"
 	"github.com/stretchr/testify/suite"
 )
 
@@ -135,6 +153,14 @@ func (s *AppTestSuite) TestVerify() {
 	app4.StronglyAcked(hash)
 	app4.TotalOrderingDeliver(common.Hashes{hash}, false)
 	s.deliverBlockWithTimeFromSequenceLength(app4, hash)
+	// Notary ack on unknown block.
+	app5 := NewApp()
+	s.setupAppByTotalOrderDeliver(app5, s.to1)
+	app5.NotaryAckDeliver(&types.NotaryAck{
+		Hash:            common.NewRandomHash(),
+		NotaryBlockHash: common.NewRandomHash(),
+	})
+	req.Equal(ErrNotaryAckUnknownBlock, app5.Verify())
 }
 
 func TestApp(t *testing.T) {