diff --git a/watchtower/wtdb/mock.go b/watchtower/wtdb/mock.go
new file mode 100644
index 000000000..e7d713966
--- /dev/null
+++ b/watchtower/wtdb/mock.go
@@ -0,0 +1,57 @@
+// +build dev
+
+package wtdb
+
+import "sync"
+
+type MockDB struct {
+	mu       sync.Mutex
+	sessions map[SessionID]*SessionInfo
+}
+
+func NewMockDB() *MockDB {
+	return &MockDB{
+		sessions: make(map[SessionID]*SessionInfo),
+	}
+}
+
+func (db *MockDB) InsertStateUpdate(update *SessionStateUpdate) (uint16, error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	info, ok := db.sessions[update.ID]
+	if !ok {
+		return 0, ErrSessionNotFound
+	}
+
+	err := info.AcceptUpdateSequence(update.SeqNum, update.LastApplied)
+	if err != nil {
+		return info.LastApplied, err
+	}
+
+	return info.LastApplied, nil
+}
+
+func (db *MockDB) GetSessionInfo(id *SessionID) (*SessionInfo, error) {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if info, ok := db.sessions[*id]; ok {
+		return info, nil
+	}
+
+	return nil, ErrSessionNotFound
+}
+
+func (db *MockDB) InsertSessionInfo(info *SessionInfo) error {
+	db.mu.Lock()
+	defer db.mu.Unlock()
+
+	if _, ok := db.sessions[info.ID]; ok {
+		return ErrSessionAlreadyExists
+	}
+
+	db.sessions[info.ID] = info
+
+	return nil
+}