diff --git a/engine/storage_interface_test.go b/engine/storage_interface_test.go
new file mode 100644
index 000000000..ef017d481
--- /dev/null
+++ b/engine/storage_interface_test.go
@@ -0,0 +1,268 @@
+/*
+Real-time Online/Offline Charging System (OCS) for Telecom & ISP environments
+Copyright (C) ITsysCOM GmbH
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>
+*/
+
+package engine
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/ugorji/go/codec"
+	"go.mongodb.org/mongo-driver/bson"
+)
+
+func TestBSONMarshal(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    interface{}
+		expected bson.D
+	}{
+		{
+			name:     "Marshal struct",
+			input:    struct{ Name string }{Name: "Cgrates"},
+			expected: bson.D{{Key: "name", Value: "Cgrates"}},
+		},
+		{
+			name:     "Marshal map",
+			input:    map[string]interface{}{"port": int32(2012)},
+			expected: bson.D{{Key: "port", Value: int32(2012)}},
+		},
+	}
+
+	marshaler := BSONMarshaler{}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := marshaler.Marshal(tt.input)
+			if err != nil {
+				t.Errorf("Marshal() error = %v, wantErr false", err)
+				return
+			}
+			var gotDoc bson.D
+			err = bson.Unmarshal(got, &gotDoc)
+			if err != nil {
+				t.Errorf("Failed to unmarshal BSON bytes: %v", err)
+				return
+			}
+			if !reflect.DeepEqual(gotDoc, tt.expected) {
+				t.Errorf("Marshal() got = %v, want %v", gotDoc, tt.expected)
+			}
+		})
+	}
+}
+
+func TestBSONMarshalUnmarshal(t *testing.T) {
+	marshaler := BSONMarshaler{}
+
+	type TestStruct struct {
+		Name string
+		Port int
+	}
+	originalStruct := TestStruct{Name: "Cgrates", Port: 2012}
+	data, err := marshaler.Marshal(originalStruct)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var resultStruct TestStruct
+	err = marshaler.Unmarshal(data, &resultStruct)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+	if !reflect.DeepEqual(originalStruct, resultStruct) {
+		t.Fatalf("Unmarshal() got = %v, want %v", resultStruct, originalStruct)
+	}
+
+	originalMap := map[string]interface{}{"name": "Cgrates", "port": int32(2012)}
+	data, err = marshaler.Marshal(originalMap)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var resultMap map[string]interface{}
+	err = marshaler.Unmarshal(data, &resultMap)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+	if !reflect.DeepEqual(originalMap, resultMap) {
+		t.Fatalf("Unmarshal() got = %v, want %v", resultMap, originalMap)
+	}
+}
+
+func TestGOBUnmarshal(t *testing.T) {
+	marshaler := GOBMarshaler{}
+
+	type TestStruct struct {
+		Name string
+		Port int
+	}
+	originalStruct := TestStruct{Name: "Cgrates", Port: 2012}
+
+	data, err := marshaler.Marshal(originalStruct)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var resultStruct TestStruct
+	err = marshaler.Unmarshal(data, &resultStruct)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(originalStruct, resultStruct) {
+		t.Fatalf("Unmarshal() got = %v, want %v", resultStruct, originalStruct)
+	}
+
+	originalMap := map[string]interface{}{"name": "Cgrates", "port": 2012}
+
+	data, err = marshaler.Marshal(originalMap)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var resultMap map[string]interface{}
+	err = marshaler.Unmarshal(data, &resultMap)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(originalMap, resultMap) {
+		t.Fatalf("Unmarshal() got = %v, want %v", resultMap, originalMap)
+	}
+}
+
+func TestBincUnmarshal(t *testing.T) {
+
+	bh := &codec.BincHandle{}
+	marshaler := BincMarshaler{bh: bh}
+
+	type TestData struct {
+		Name string
+		Port int
+	}
+	original := TestData{Name: "Cgrates", Port: 2012}
+	data, err := marshaler.Marshal(original)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var result TestData
+	err = marshaler.Unmarshal(data, &result)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(original, result) {
+		t.Errorf("Unmarshal() got = %v, want %v", result, original)
+	}
+}
+
+func TestNewBincMarshaler(t *testing.T) {
+	marshaler := NewBincMarshaler()
+	type TestData struct {
+		Name string
+		Port int
+	}
+	original := TestData{Name: "Cgrates", Port: 2012}
+
+	data, err := marshaler.Marshal(original)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var result TestData
+	err = marshaler.Unmarshal(data, &result)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(original, result) {
+		t.Errorf("Unmarshal() got = %v, want %v", result, original)
+	}
+}
+
+func TestJSONBufUnmarshal(t *testing.T) {
+
+	marshaler := JSONBufMarshaler{}
+
+	type TestData struct {
+		Name string
+		Port int
+	}
+	original := TestData{Name: "Cgrates", Port: 2012}
+
+	data, err := json.Marshal(original)
+	if err != nil {
+		t.Fatalf("json.Marshal() error = %v", err)
+	}
+
+	var result TestData
+	err = marshaler.Unmarshal(data, &result)
+	if err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(original, result) {
+		t.Errorf("Unmarshal() got = %v, want %v", result, original)
+	}
+}
+
+func TestJSONBufMarshal(t *testing.T) {
+
+	marshaler := JSONBufMarshaler{}
+
+	type TestData struct {
+		Name string
+		Port int
+	}
+	original := TestData{Name: "Cgrates", Port: 2012}
+
+	data, err := marshaler.Marshal(original)
+	if err != nil {
+		t.Fatalf("Marshal() error = %v", err)
+	}
+
+	var result TestData
+	err = json.Unmarshal(data, &result)
+	if err != nil {
+		t.Fatalf("json.Unmarshal() error = %v", err)
+	}
+
+	if !reflect.DeepEqual(original, result) {
+		t.Errorf("Marshal() and Unmarshal() mismatch. Got = %v, want %v", result, original)
+	}
+}
+
+func TestNewMarshalerUnsupported(t *testing.T) {
+
+	m, err := NewMarshaler("Unknown")
+
+	if err == nil {
+		t.Errorf("Expected error, got nil")
+	}
+
+	if m != nil {
+		t.Errorf("Expected Marshaler to be nil, got %+v", m)
+	}
+
+	expectedErrMsg := "Unsupported marshaler: Unknown"
+	if err.Error() != expectedErrMsg {
+		t.Errorf("Expected error message '%s', got '%s'", expectedErrMsg, err.Error())
+	}
+}