diff --git a/src/main.ts b/src/main.ts
index 48a0570..46351bf 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -10,7 +10,7 @@ const xmlDeclaration = '<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet t
 const xmlns = 'http://www.sitemaps.org/schemas/sitemap/0.9'
 
 class SitemapManager {
-  options: Options
+  options: FullOptions
   #urlDatas: {
     [category: string]: string
   } = {}
@@ -18,7 +18,15 @@ class SitemapManager {
   #isFinished: Boolean = false
 
   constructor (options: Options) {
-    this.options = options
+    this.options = {
+      outDir: options.outDir || './public',
+      siteURL: options.siteURL,
+      pathPrefix: options.pathPrefix || '',
+      hooks: {
+        warningHandler: options.hooks?.warningHandler || utils.defaultHookSet.defaultWarningHandler,
+        fileHandler: options.hooks?.fileHandler || utils.defaultHookSet.defaultFileHandler
+      }
+    }
   }
 
   addUrl (category: string, url: UrlObj[] | UrlObj): void {
@@ -40,7 +48,7 @@ class SitemapManager {
         xmlContents = xmlContents + `<sitemap>${utils.objToString({ loc: new URL(path.join(this.options.pathPrefix || '', `sitemap-${category}.xml`), this.options.siteURL), lastmod: new Date() })}</sitemap>`
       }
       try {
-        fs.writeFileSync(
+        this.options.hooks.fileHandler(
           path.resolve(this.options?.outDir || './public', 'sitemap.xml'),
           xmlDeclaration + `<sitemapindex xmlns="${xmlns}">${xmlContents}</sitemapindex>`
         )
diff --git a/src/types.ts b/src/types.ts
index 501618f..4088fa8 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,9 +1,29 @@
 import { URL } from 'url'
 
+export type WarningHandler = (msg: string) => void
+
+export type FileHandler = (file: string, data: string) => void
+
+interface HookSet {
+  warningHandler?: WarningHandler,
+  fileHandler?: FileHandler
+}
+
+export interface FullOptions {
+  outDir: string,
+  siteURL: string,
+  pathPrefix: string,
+  hooks: {
+    warningHandler: WarningHandler,
+    fileHandler: FileHandler
+  }
+}
+
 export interface Options {
   outDir?: string,
   siteURL: string,
-  pathPrefix?: string
+  pathPrefix?: string,
+  hooks?: HookSet
 }
 
 export interface UrlObj {
diff --git a/src/utils.ts b/src/utils.ts
index 035ccab..d32908a 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,7 +1,19 @@
-import { UrlObj } from './types'
+import { UrlObj, WarningHandler, FileHandler } from './types'
+import * as fs from 'fs'
 
 const freqMap = ['', 'never', 'yearly', 'monthly', 'weekly', 'daily', 'hourly', 'always']
 
+const defaultWarningHandler: WarningHandler = (msg) => {
+  throw new Error(msg)
+}
+
+const defaultFileHandler: FileHandler = fs.writeFileSync
+
+export const defaultHookSet = {
+  defaultWarningHandler,
+  defaultFileHandler
+}
+
 export function dateConverter (date: Date | string): string {
   return new Date(date).toISOString()
 }