diff --git a/go.mod b/go.mod
index ec2fce562..9abb9dd77 100644
--- a/go.mod
+++ b/go.mod
@@ -18,7 +18,7 @@ require (
 	github.com/spf13/cobra v1.5.0
 	github.com/spf13/viper v1.17.0
 	github.com/stretchr/testify v1.9.0
-	github.com/undefinedlabs/go-mpatch v1.0.6
+	github.com/undefinedlabs/go-mpatch v1.0.7
 	go.mongodb.org/mongo-driver v1.11.7
 	go.uber.org/zap v1.23.0
 	golang.org/x/crypto v0.16.0
@@ -30,6 +30,8 @@ require (
 	gopkg.in/yaml.v3 v3.0.1
 )
 
+require github.com/stretchr/objx v0.5.2 // indirect
+
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
diff --git a/go.sum b/go.sum
index 10b9cb034..77e3fa764 100644
--- a/go.sum
+++ b/go.sum
@@ -318,6 +318,8 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
@@ -336,6 +338,8 @@ github.com/tidwall/pretty v1.0.0 h1:HsD+QiTn7sK6flMKIvNmpqz1qrpP3Ps6jOKIKMooyg4=
 github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
 github.com/undefinedlabs/go-mpatch v1.0.6 h1:h8q5ORH/GaOE1Se1DMhrOyljXZEhRcROO7agMqWXCOY=
 github.com/undefinedlabs/go-mpatch v1.0.6/go.mod h1:TyJZDQ/5AgyN7FSLiBJ8RO9u2c6wbtRvK827b6AVqY4=
+github.com/undefinedlabs/go-mpatch v1.0.7 h1:943FMskd9oqfbZV0qRVKOUsXQhTLXL0bQTVbQSpzmBs=
+github.com/undefinedlabs/go-mpatch v1.0.7/go.mod h1:TyJZDQ/5AgyN7FSLiBJ8RO9u2c6wbtRvK827b6AVqY4=
 github.com/xdg-go/pbkdf2 v1.0.0 h1:Su7DPu48wXMwC3bs7MCNG+z4FhcyEuz5dlvchbq0B0c=
 github.com/xdg-go/pbkdf2 v1.0.0/go.mod h1:jrpuAogTd400dnrH08LKmI/xc1MbPOebTwRqcT5RDeI=
 github.com/xdg-go/scram v1.1.1 h1:VOMT+81stJgXW3CpHyqHN3AXDYIMsx56mEFrB37Mb/E=
diff --git a/server/packs/packs_test.go b/server/packs/packs_test.go
new file mode 100644
index 000000000..42a85b642
--- /dev/null
+++ b/server/packs/packs_test.go
@@ -0,0 +1,314 @@
+/*
+ * Copyright 2024 The Yorkie Authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package packs_test
+
+import (
+	"context"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"testing"
+
+	"connectrpc.com/connect"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/yorkie-team/yorkie/api/converter"
+	"github.com/yorkie-team/yorkie/api/types"
+	api "github.com/yorkie-team/yorkie/api/yorkie/v1"
+	"github.com/yorkie-team/yorkie/api/yorkie/v1/v1connect"
+	"github.com/yorkie-team/yorkie/client"
+	"github.com/yorkie-team/yorkie/pkg/document"
+	"github.com/yorkie-team/yorkie/pkg/document/time"
+	"github.com/yorkie-team/yorkie/server/backend"
+	"github.com/yorkie-team/yorkie/server/backend/database"
+	"github.com/yorkie-team/yorkie/server/backend/database/mongo"
+	"github.com/yorkie-team/yorkie/server/backend/housekeeping"
+	"github.com/yorkie-team/yorkie/server/clients"
+	"github.com/yorkie-team/yorkie/server/documents"
+	"github.com/yorkie-team/yorkie/server/packs"
+	"github.com/yorkie-team/yorkie/server/profiling/prometheus"
+	"github.com/yorkie-team/yorkie/server/rpc"
+	"github.com/yorkie-team/yorkie/test/helper"
+)
+
+var (
+	// ErrUpdateClientInfoFailed occurs when updating ClientInfo failed
+	// for testing purposes.
+	ErrUpdateClientInfoFailed = errors.New("updating clientinfo failed")
+)
+
+var (
+	testRPCServer *rpc.Server
+	testRPCAddr   = fmt.Sprintf("localhost:%d", helper.RPCPort)
+	testClient    v1connect.YorkieServiceClient
+	testBackend   *backend.Backend
+	testMockDB    *MockDB
+)
+
+// MockDB represents a mock database for testing purposes
+type MockDB struct {
+	database.Database
+	mockUpdateClientInfoAfterPushPull func(context.Context, *database.ClientInfo, *database.DocInfo) error
+}
+
+// NewMockDB returns a mock database with a real database
+func NewMockDB(database database.Database) *MockDB {
+	return &MockDB{
+		Database: database,
+	}
+}
+
+func (m *MockDB) UpdateClientInfoAfterPushPull(
+	ctx context.Context,
+	clientInfo *database.ClientInfo,
+	docInfo *database.DocInfo,
+) error {
+	if m.mockUpdateClientInfoAfterPushPull != nil {
+		return m.mockUpdateClientInfoAfterPushPull(ctx, clientInfo, docInfo)
+	}
+	return m.Database.UpdateClientInfoAfterPushPull(ctx, clientInfo, docInfo)
+}
+
+func TestMain(m *testing.M) {
+	met, err := prometheus.NewMetrics()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	testBackend, err = backend.New(
+		&backend.Config{
+			AdminUser:                 helper.AdminUser,
+			AdminPassword:             helper.AdminPassword,
+			UseDefaultProject:         helper.UseDefaultProject,
+			ClientDeactivateThreshold: helper.ClientDeactivateThreshold,
+			SnapshotThreshold:         helper.SnapshotThreshold,
+			AuthWebhookCacheSize:      helper.AuthWebhookSize,
+			ProjectInfoCacheSize:      helper.ProjectInfoCacheSize,
+			ProjectInfoCacheTTL:       helper.ProjectInfoCacheTTL.String(),
+			AdminTokenDuration:        helper.AdminTokenDuration,
+		}, &mongo.Config{
+			ConnectionURI:     helper.MongoConnectionURI,
+			YorkieDatabase:    helper.TestDBName(),
+			ConnectionTimeout: helper.MongoConnectionTimeout,
+			PingTimeout:       helper.MongoPingTimeout,
+		}, &housekeeping.Config{
+			Interval:                  helper.HousekeepingInterval.String(),
+			CandidatesLimitPerProject: helper.HousekeepingCandidatesLimitPerProject,
+			ProjectFetchSize:          helper.HousekeepingProjectFetchSize,
+		}, met,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	testMockDB = NewMockDB(testBackend.DB)
+	testBackend.DB = testMockDB
+
+	project, err := testBackend.DB.FindProjectInfoByID(
+		context.Background(),
+		database.DefaultProjectID,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	testRPCServer, err = rpc.NewServer(
+		&rpc.Config{
+			Port: helper.RPCPort,
+		}, testBackend,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if err = testRPCServer.Start(); err != nil {
+		log.Fatalf("failed rpc listen: %s\n", err)
+	}
+	if err = helper.WaitForServerToStart(testRPCAddr); err != nil {
+		log.Fatal(err)
+	}
+
+	authInterceptor := client.NewAuthInterceptor(project.PublicKey, "")
+
+	conn := http.DefaultClient
+	testClient = v1connect.NewYorkieServiceClient(
+		conn,
+		"http://"+testRPCAddr,
+		connect.WithInterceptors(authInterceptor),
+	)
+
+	code := m.Run()
+
+	if err := testBackend.Shutdown(); err != nil {
+		log.Fatal(err)
+	}
+	testRPCServer.Shutdown(true)
+	os.Exit(code)
+}
+
+func triggerErrUpdateClientInfo(on bool) {
+	if on {
+		testMockDB.mockUpdateClientInfoAfterPushPull = func(
+			context.Context,
+			*database.ClientInfo,
+			*database.DocInfo,
+		) error {
+			return ErrUpdateClientInfoFailed
+		}
+	} else {
+		testMockDB.mockUpdateClientInfoAfterPushPull = nil
+	}
+}
+
+func TestPacks(t *testing.T) {
+	t.Run("cannot detect change duplication due to clientInfo update failure", func(t *testing.T) {
+		t.Skip("remove this after resolving pushpull consistency problem")
+		ctx := context.Background()
+
+		projectInfo, err := testBackend.DB.FindProjectInfoByID(
+			ctx,
+			database.DefaultProjectID,
+		)
+		assert.NoError(t, err)
+		project := projectInfo.ToProject()
+
+		triggerErrUpdateClientInfo(false)
+
+		activateResp, err := testClient.ActivateClient(
+			context.Background(),
+			connect.NewRequest(&api.ActivateClientRequest{ClientKey: helper.TestDocKey(t).String()}))
+		assert.NoError(t, err)
+
+		clientID, _ := hex.DecodeString(activateResp.Msg.ClientId)
+		resPack, err := testClient.AttachDocument(
+			context.Background(),
+			connect.NewRequest(&api.AttachDocumentRequest{
+				ClientId: activateResp.Msg.ClientId,
+				ChangePack: &api.ChangePack{
+					DocumentKey: helper.TestDocKey(t).String(),
+					Checkpoint:  &api.Checkpoint{ServerSeq: 0, ClientSeq: 1},
+					Changes: []*api.Change{
+						{
+							Id: &api.ChangeID{
+								ClientSeq: 1,
+								Lamport:   1,
+								ActorId:   clientID,
+							},
+						},
+					},
+				},
+			},
+			))
+		assert.NoError(t, err)
+
+		actorID, err := time.ActorIDFromBytes(clientID)
+		assert.NoError(t, err)
+
+		docID := types.ID(resPack.Msg.DocumentId)
+		docRefKey := types.DocRefKey{
+			ProjectID: project.ID,
+			DocID:     docID,
+		}
+
+		// 0. Check docInfo.ServerSeq and clientInfo.Checkpoint
+		docInfo, err := documents.FindDocInfoByRefKey(ctx, testBackend, docRefKey)
+		assert.NoError(t, err)
+		assert.Equal(t, int64(1), docInfo.ServerSeq)
+
+		clientInfo, err := clients.FindActiveClientInfo(ctx, testBackend.DB, types.ClientRefKey{
+			ProjectID: project.ID,
+			ClientID:  types.IDFromActorID(actorID),
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, int64(1), clientInfo.Checkpoint(docID).ServerSeq)
+		assert.Equal(t, uint32(1), clientInfo.Checkpoint(docID).ClientSeq)
+
+		// 1. Create a ChangePack with a single Change
+		pack, err := converter.FromChangePack(&api.ChangePack{
+			DocumentKey: helper.TestDocKey(t).String(),
+			Checkpoint:  &api.Checkpoint{ServerSeq: 0, ClientSeq: 2},
+			Changes: []*api.Change{
+				{
+					Id: &api.ChangeID{
+						ClientSeq: 2,
+						Lamport:   2,
+						ActorId:   clientID,
+					},
+				},
+			},
+		})
+		assert.NoError(t, err)
+
+		// 2-1. An arbitrary failure occurs while updating clientInfo
+		triggerErrUpdateClientInfo(true)
+
+		_, err = packs.PushPull(ctx, testBackend, project, clientInfo, docInfo, pack, packs.PushPullOptions{
+			Mode:   types.SyncModePushPull,
+			Status: document.StatusAttached,
+		})
+		assert.ErrorIs(t, err, ErrUpdateClientInfoFailed)
+
+		triggerErrUpdateClientInfo(false)
+
+		// 2-2. pushed change is stored in the database
+		changes, err := packs.FindChanges(ctx, testBackend, docInfo, 2, 2)
+		assert.NoError(t, err)
+		assert.Len(t, changes, 1)
+
+		// 2-3. docInfo.ServerSeq increases from 1 to 2
+		docInfo, err = documents.FindDocInfoByRefKey(ctx, testBackend, docRefKey)
+		assert.NoError(t, err)
+		assert.Equal(t, int64(2), docInfo.ServerSeq)
+
+		// 2-4. clientInfo.Checkpoint has not been updated
+		clientInfo, err = clients.FindActiveClientInfo(ctx, testBackend.DB, types.ClientRefKey{
+			ProjectID: project.ID,
+			ClientID:  types.IDFromActorID(actorID),
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, int64(1), clientInfo.Checkpoint(docID).ServerSeq)
+		assert.Equal(t, uint32(1), clientInfo.Checkpoint(docID).ClientSeq)
+
+		// 3-1. A duplicate request is sent
+		_, err = packs.PushPull(ctx, testBackend, project, clientInfo, docInfo, pack, packs.PushPullOptions{
+			Mode:   types.SyncModePushPull,
+			Status: document.StatusAttached,
+		})
+		assert.NoError(t, err)
+
+		// 3-2. duplicated change is not stored in the database
+		changes, err = packs.FindChanges(ctx, testBackend, docInfo, 3, 3)
+		assert.NoError(t, err)
+		assert.Len(t, changes, 0)
+
+		// 3-3. The server should detect the duplication and not update docInfo.ServerSeq
+		docInfo, err = documents.FindDocInfoByRefKey(ctx, testBackend, docRefKey)
+		assert.NoError(t, err)
+		assert.Equal(t, int64(2), docInfo.ServerSeq)
+
+		// 3-4. clientInfo.Checkpoint has been updated properly
+		clientInfo, err = clients.FindActiveClientInfo(ctx, testBackend.DB, types.ClientRefKey{
+			ProjectID: project.ID,
+			ClientID:  types.IDFromActorID(actorID),
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, int64(2), clientInfo.Checkpoint(docID).ServerSeq)
+		assert.Equal(t, uint32(2), clientInfo.Checkpoint(docID).ClientSeq)
+	})
+}