diff --git a/database.go b/database.go
index a1c7243..c59f12a 100644
--- a/database.go
+++ b/database.go
@@ -62,18 +62,23 @@ func (db *Database) Start() {
 }
 
 func (db *Database) WALStatus() (ws WALStatus) {
-	ws.MaxID = db.kv.WALMaxSeqNum()
-	ws.MaxAppliedID = db.kv.MaxSeqNum()
+	ws.MaxSeqNumKV = db.kv.WALMaxSeqNum()
+	ws.MaxSeqNumWAL = db.kv.MaxSeqNum()
 	return
 }
 
 func (db *Database) Close() {
-	db.kv.Close()
-	db.lock.Close()
+	if db.kv != nil {
+		db.kv.Close()
+		db.kv = nil
+	}
+	if db.lock != nil {
+		db.lock.Close()
+		db.lock = nil
+	}
 }
 
-// -----------------
-		db.kv = kvstore.NewSecondary(root)-----------------------------------------------------------
+// ----------------------------------------------------------------------------
 
 func (db *Database) onStore(collection string, id uint64, data []byte) {
 	c, ok := db.collections[collection]
diff --git a/database_test.go b/database_test.go
index 6c8376d..5a828bc 100644
--- a/database_test.go
+++ b/database_test.go
@@ -5,7 +5,7 @@ import "time"
 func (db *Database) waitForWAL() {
 	for {
 		status := db.WALStatus()
-		if status.MaxAppliedID == status.MaxID {
+		if status.MaxSeqNumWAL == status.MaxSeqNumKV {
 			return
 		}
 		time.Sleep(100 * time.Millisecond)
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..0002bea
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,13 @@
+package mdb
+
+import (
+	"math/rand"
+	"os"
+	"testing"
+	"time"
+)
+
+func TestMain(m *testing.M) {
+	rand.Seed(time.Now().UnixNano())
+	os.Exit(m.Run())
+}
diff --git a/types.go b/types.go
index 3600684..9baa3eb 100644
--- a/types.go
+++ b/types.go
@@ -1,8 +1,8 @@
 package mdb
 
 type WALStatus struct {
-	MaxID        uint64 // TODO: WALMaxSeqNum
-	MaxAppliedID uint64 // TODO: KVMaxSeqNum
+	MaxSeqNumKV  uint64
+	MaxSeqNumWAL uint64
 }
 
 type itemIndex[T any] interface {