1 files changed, 19 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
 }