diff --git a/src/app/components/home.test.tsx b/src/app/components/home.test.tsx
index cce6bf3..fdeaddb 100644
--- a/src/app/components/home.test.tsx
+++ b/src/app/components/home.test.tsx
@@ -5,7 +5,7 @@ import {
 import { render } from '@testing-library/react'
 import '@testing-library/jest-dom'
 import { HomePageUIService } from './home'
-import { QuestionSetRepoFactory } from '../../repo/question_set'
+import { LocalStorageQuestionSetRepo } from '../../repo/question_set'
 
 describe('HomePage', () => {
   // Detail of testing of the navigation of this page should be in the integration test combine with saving question set
@@ -51,9 +51,7 @@ function renderHomePage({
 }: {
   questionSets: readonly QuestionSet[]
 }) {
-  const questionSetRepo = QuestionSetRepoFactory.createTestInstance()
+  const questionSetRepo = LocalStorageQuestionSetRepo.createNull()
   questionSets.forEach((set) => questionSetRepo.addQuestionSet(set))
-  return render(
-    HomePageUIService.createTestInstance({ questionSetRepo }).getElement(),
-  )
+  return render(HomePageUIService.createNull({ questionSetRepo }).getElement())
 }
diff --git a/src/app/components/home.tsx b/src/app/components/home.tsx
index c18a1d1..b6328bb 100644
--- a/src/app/components/home.tsx
+++ b/src/app/components/home.tsx
@@ -4,7 +4,7 @@ import { useRouter } from 'next/navigation'
 import { QuestionSet } from '../../model/question_set'
 import {
   QuestionSetRepo,
-  QuestionSetRepoFactory,
+  LocalStorageQuestionSetRepo,
 } from '../../repo/question_set'
 import { useEffect, useState } from 'react'
 import LoadingSpinner from './loading'
@@ -12,12 +12,12 @@ import LoadingSpinner from './loading'
 export class HomePageUIService {
   static create() {
     return new HomePageUIService({
-      questionSetRepo: QuestionSetRepoFactory.createLocalStorageInstance(),
+      questionSetRepo: LocalStorageQuestionSetRepo.create(),
     })
   }
 
-  static createTestInstance({
-    questionSetRepo = QuestionSetRepoFactory.createTestInstance(),
+  static createNull({
+    questionSetRepo = LocalStorageQuestionSetRepo.createNull(),
   }) {
     return new HomePageUIService({ questionSetRepo })
   }
diff --git a/src/app/components/mc/editor.test.tsx b/src/app/components/mc/editor.test.tsx
index 18e3d91..2ac48a1 100644
--- a/src/app/components/mc/editor.test.tsx
+++ b/src/app/components/mc/editor.test.tsx
@@ -1,7 +1,7 @@
 import { fireEvent, render, screen } from '@testing-library/react'
 import {
   QuestionSetRepo,
-  QuestionSetRepoFactory,
+  LocalStorageQuestionSetRepo,
 } from '../../../repo/question_set'
 import {
   QuestionSetEditorAriaLabel,
@@ -18,11 +18,11 @@ class UIServiceInteractor {
 
   constructor({
     questionSetName = 'Dummy name',
-    questionSetRepo = QuestionSetRepoFactory.createTestInstance(),
+    questionSetRepo = LocalStorageQuestionSetRepo.createNull(),
   }) {
     this.questionSetRepo = questionSetRepo
     render(
-      QuestionSetEditorUIService.createTestInstance({
+      QuestionSetEditorUIService.createNull({
         questionSetRepo: this.questionSetRepo,
       }).getElement(),
     )
@@ -465,7 +465,7 @@ describe('QuestionSetEditorUIService', () => {
   })
 
   it('should not save if same name as existing question set', () => {
-    const questionSetRepo = QuestionSetRepoFactory.createTestInstance()
+    const questionSetRepo = LocalStorageQuestionSetRepo.createNull()
     const questionSet = new QuestionSetBuilderForTest()
       .setName('Test name')
       .appendQuestion()
diff --git a/src/app/components/mc/editor.tsx b/src/app/components/mc/editor.tsx
index 0be5da9..22b9c35 100644
--- a/src/app/components/mc/editor.tsx
+++ b/src/app/components/mc/editor.tsx
@@ -3,7 +3,7 @@
 import { useState } from 'react'
 import {
   QuestionSetRepo,
-  QuestionSetRepoFactory,
+  LocalStorageQuestionSetRepo,
   AddQuestionSetError,
 } from '../../../repo/question_set'
 import { Question, QuestionSet } from '../../../model/question_set'
@@ -49,12 +49,14 @@ export class QuestionSetEditorAriaLabel {
 export class QuestionSetEditorUIService {
   static create() {
     return new QuestionSetEditorUIService({
-      questionSetRepo: QuestionSetRepoFactory.createLocalStorageInstance(),
+      questionSetRepo: LocalStorageQuestionSetRepo.create(),
     })
   }
 
-  static createTestInstance({
-    questionSetRepo = QuestionSetRepoFactory.createTestInstance(),
+  static createNull({
+    questionSetRepo = LocalStorageQuestionSetRepo.createNull(),
+  }: {
+    questionSetRepo?: QuestionSetRepo
   }) {
     return new QuestionSetEditorUIService({ questionSetRepo })
   }
diff --git a/src/app/components/mc/quiz.test.tsx b/src/app/components/mc/quiz.test.tsx
index e298a7b..b105a05 100644
--- a/src/app/components/mc/quiz.test.tsx
+++ b/src/app/components/mc/quiz.test.tsx
@@ -6,7 +6,7 @@ import {
   QuestionSetBuilderForTest,
   QuestionSet,
 } from '../../../model/question_set'
-import { QuestionSetRepoFactory } from '../../../repo/question_set'
+import { LocalStorageQuestionSetRepo } from '../../../repo/question_set'
 
 describe('MultipleChoiceQuiz', () => {
   const presetCorrectChoiceMcBuilder = () => {
@@ -109,7 +109,7 @@ describe('MultipleChoiceQuiz', () => {
 
   it("should render not found when question set doesn't exist", () => {
     const { getByText } = render(
-      MultipleChoiceQuizUIService.createTestInstance({
+      MultipleChoiceQuizUIService.createNull({
         questionSetId: 'unknown',
       }).getElement(),
     )
@@ -123,10 +123,10 @@ function renderMultipleChoicePage({
 }: {
   questionSet: QuestionSet
 }) {
-  const questionSetRepo = QuestionSetRepoFactory.createTestInstance()
+  const questionSetRepo = LocalStorageQuestionSetRepo.createNull()
   questionSetRepo.addQuestionSet(questionSet)
   return render(
-    MultipleChoiceQuizUIService.createTestInstance({
+    MultipleChoiceQuizUIService.createNull({
       questionSetRepo,
       questionSetId: questionSet.id,
     }).getElement(),
diff --git a/src/app/components/mc/quiz.tsx b/src/app/components/mc/quiz.tsx
index efbcc7d..3534213 100644
--- a/src/app/components/mc/quiz.tsx
+++ b/src/app/components/mc/quiz.tsx
@@ -5,7 +5,7 @@ import { Question, QuestionSet } from '../../../model/question_set'
 import {
   GetQuestionSetError,
   QuestionSetRepo,
-  QuestionSetRepoFactory,
+  LocalStorageQuestionSetRepo,
 } from '../../../repo/question_set'
 import LoadingSpinner from '../loading'
 import Error from 'next/error'
@@ -13,13 +13,13 @@ import Error from 'next/error'
 export class MultipleChoiceQuizUIService {
   static create({ questionSetId }: { questionSetId: string }) {
     return new MultipleChoiceQuizUIService({
-      questionSetRepo: QuestionSetRepoFactory.createLocalStorageInstance(),
+      questionSetRepo: LocalStorageQuestionSetRepo.create(),
       questionSetId,
     })
   }
 
-  static createTestInstance({
-    questionSetRepo = QuestionSetRepoFactory.createTestInstance(),
+  static createNull({
+    questionSetRepo = LocalStorageQuestionSetRepo.createNull(),
     questionSetId,
   }: {
     questionSetRepo?: QuestionSetRepo
diff --git a/src/repo/question_set.test.ts b/src/repo/question_set.test.ts
index 1353294..3635651 100644
--- a/src/repo/question_set.test.ts
+++ b/src/repo/question_set.test.ts
@@ -14,7 +14,7 @@ describe('LocalStorageQuestionSetRepo', () => {
   let questionSet: QuestionSet
 
   beforeEach(() => {
-    repo = LocalStorageQuestionSetRepo.createTestInstance()
+    repo = LocalStorageQuestionSetRepo.createNull()
     questionSet = new QuestionSetBuilderForTest()
       .appendQuestion({
         mc: new MultipleChoiceBuilder()
diff --git a/src/repo/question_set.ts b/src/repo/question_set.ts
index 8384c50..2ce9d7a 100644
--- a/src/repo/question_set.ts
+++ b/src/repo/question_set.ts
@@ -1,6 +1,6 @@
 import { QuestionSet } from '../model/question_set'
 import { CustomBaseError } from '../utils/err'
-import { LocalStorageObjectOperator } from '../utils/local_storage'
+import { LocalStorageOperator } from '../utils/local_storage'
 
 export interface QuestionSetRepo {
   /**
@@ -38,38 +38,26 @@ export class GetQuestionSetError extends CustomBaseError<GetQuestionSetErrorCode
   }
 }
 
-export class QuestionSetRepoFactory {
-  static createTestInstance(): QuestionSetRepo {
-    return LocalStorageQuestionSetRepo.createTestInstance()
-  }
-
-  static createLocalStorageInstance(): QuestionSetRepo {
-    return LocalStorageQuestionSetRepo.create()
-  }
-}
-
 export class LocalStorageQuestionSetRepo implements QuestionSetRepo {
   static readonly STORAGE_PATH = 'questionSets'
 
-  static createTestInstance(): LocalStorageQuestionSetRepo {
+  static createNull(): LocalStorageQuestionSetRepo {
     return new LocalStorageQuestionSetRepo(
-      LocalStorageObjectOperator.createTestInstance(this.STORAGE_PATH),
+      LocalStorageOperator.createNull(this.STORAGE_PATH),
     )
   }
 
   static create(): LocalStorageQuestionSetRepo {
     return new LocalStorageQuestionSetRepo(
-      LocalStorageObjectOperator.create(this.STORAGE_PATH),
+      LocalStorageOperator.create(this.STORAGE_PATH),
     )
   }
 
-  private constructor(
-    localStorageObjectOperator: LocalStorageObjectOperator<QuestionSet>,
-  ) {
-    this.localStorageOperator = localStorageObjectOperator
+  private constructor(localStorageOperator: LocalStorageOperator<QuestionSet>) {
+    this.localStorageOperator = localStorageOperator
   }
 
-  private localStorageOperator: LocalStorageObjectOperator<QuestionSet>
+  private localStorageOperator: LocalStorageOperator<QuestionSet>
 
   addQuestionSet(questionSet: QuestionSet): void {
     if (
diff --git a/src/utils/local_storage.ts b/src/utils/local_storage.ts
index d44864b..b6aaffc 100644
--- a/src/utils/local_storage.ts
+++ b/src/utils/local_storage.ts
@@ -27,21 +27,13 @@ class LocalStorageWrapperImpl implements LocalStorageWrapper {
   }
 }
 
-export class LocalStorageObjectOperator<T> {
-  static create<T>(storagePath: string): LocalStorageObjectOperator<T> {
-    return new LocalStorageObjectOperator(
-      new LocalStorageWrapperImpl(),
-      storagePath,
-    )
+export class LocalStorageOperator<T> {
+  static create<T>(storagePath: string): LocalStorageOperator<T> {
+    return new LocalStorageOperator(new LocalStorageWrapperImpl(), storagePath)
   }
 
-  static createTestInstance<T>(
-    storagePath: string,
-  ): LocalStorageObjectOperator<T> {
-    return new LocalStorageObjectOperator(
-      new FakeLocalStorageWrapper(),
-      storagePath,
-    )
+  static createNull<T>(storagePath: string): LocalStorageOperator<T> {
+    return new LocalStorageOperator(new FakeLocalStorageWrapper(), storagePath)
   }
 
   private constructor(