diff --git a/lib/formatter.js b/lib/formatter.js
index 2cf9dff..6df7b14 100644
--- a/lib/formatter.js
+++ b/lib/formatter.js
@@ -89,7 +89,7 @@ class Formatter {
    * @returns {string} - The content for `Rsa.sign`
    */
   static request(method, uri, timestamp, nonce, body = '') {
-    return `${method}\n${uri}\n${timestamp}\n${nonce}\n${body}\n`
+    return this.joinedByLineFeed(method, uri, timestamp, nonce, body)
   }
 
   /**
@@ -102,7 +102,40 @@ class Formatter {
    * @returns {string} - The content for `Rsa.verify`
    */
   static response(timestamp, nonce, body = '') {
-    return `${timestamp}\n${nonce}\n${body}\n`
+    return this.joinedByLineFeed(timestamp, nonce, body)
+  }
+
+  /**
+   * Joined this inputs by for `Line Feed`(LF) char.
+   *
+   * @param {string[]} pieces - The string(s) joined by line feed.
+   *
+   * @returns {string} - The joined string.
+   */
+  static joinedByLineFeed(...pieces) {
+    return [...pieces, ``].join(`\n`)
+  }
+
+  /**
+   * Sorts an Object by key.
+   *
+   * @param {object} thing - The input object.
+   *
+   * @returns {object} - The sorted object.
+   */
+  static ksort(thing) {
+    return Object.keys(thing).sort().reduce((des, key) => (des[key] = thing[key], des), {})
+  }
+
+  /**
+   * Like `queryString` does but without the `sign` and `empty value` entities.
+   *
+   * @param {object} thing - The input object.
+   *
+   * @returns {string} - The sorted object.
+   */
+  static queryStringLike(thing) {
+    return Object.entries(thing).filter(([k, v]) => k != `sign` && v !== void 0 && v !== ``).map(i => i.join(`=`)).join(`&`)
   }
 }
 
diff --git a/lib/wechatpay.js b/lib/wechatpay.js
index 7c11e28..371f8f2 100644
--- a/lib/wechatpay.js
+++ b/lib/wechatpay.js
@@ -1,6 +1,9 @@
 const axios = require('axios')
 const interceptor = require('./interceptor')
 
+/*eslint-disable-next-line*/
+const CLIENT = Symbol('CLIENT')
+
 /**
  * A Wechatpay APIv3's amazing client.
  *
@@ -46,14 +49,14 @@ class Wechatpay {
   /**
    * @property {AxiosInstance} client - The axios instance
    */
-  static get client() { return Wechatpay[CLIENT] }
-  static set client(target) { Wechatpay[CLIENT] = target }
+  static get client() { return this[CLIENT] }
+  static set client(target) { this[CLIENT] = target }
 
   /**
-   * @property {RegExp} URI_ENTITY - The URI entity which's split by slash ask `uri_template`
+   * @property {RegExp} REGEXP_URI_ENTITY - The URI entity which's split by slash ask `uri_template`
    */
   /*eslint-disable-next-line*/
-  static get URI_ENTITY() { return /^\{([^\}]+)\}$/ }
+  static get REGEXP_URI_ENTITY() { return /^\{([^\}]+)\}$/ }
 
   /**
    * Compose the `URL`.pathname based on the container's entities
@@ -76,13 +79,13 @@ class Wechatpay {
       // `camelCase` to `camel-case`
       .replace(/[A-Z]/g, w => `-${w.toLowerCase()}`)
       // `$dynamic_variable$` to `{dynamic_variable}`
-      .replace(/^\$/, `{`).replace(/\$$/, `}`)
+      .replace(/^\$(.*)\$$/, `{$1}`)
   }
 
   /**
    * @property {object} container - Client side the URIs' entity mapper
    */
-  static get container() { return {
+  static get container() { const that = this; return {
     /**
      * @property {string[]} entities - The URI entities
      */
@@ -95,8 +98,8 @@ class Wechatpay {
      */
     withEntities: function(list) {
       this.entities.forEach((one, index, src) => {
-        if (Wechatpay.URI_ENTITY.test(one)) {
-          const sign = one.replace(Wechatpay.URI_ENTITY, `$1`)
+        if (that.REGEXP_URI_ENTITY.test(one)) {
+          const sign = one.replace(that.REGEXP_URI_ENTITY, `$1`)
           src[index] = list[sign] ? list[sign] : one
         }
       })
@@ -110,7 +113,7 @@ class Wechatpay {
      * @returns {PromiseLike} - The `AxiosPromise`
      */
     get: async function(...arg) {
-      return Wechatpay.client.get(Wechatpay.pathname(this.entities), ...arg)
+      return that.client.get(that.pathname(this.entities), ...arg)
     },
 
     /**
@@ -119,7 +122,7 @@ class Wechatpay {
      * @returns {PromiseLike} - The `AxiosPromise`
      */
     post: async function(...arg) {
-      return Wechatpay.client.post(Wechatpay.pathname(this.entities), ...arg)
+      return that.client.post(that.pathname(this.entities), ...arg)
     },
 
     /**
@@ -128,7 +131,7 @@ class Wechatpay {
      * @returns {PromiseLike} - The `AxiosPromise`
      */
     put: async function(...arg) {
-      return Wechatpay.client.put(Wechatpay.pathname(this.entities), ...arg)
+      return that.client.put(that.pathname(this.entities), ...arg)
     },
 
     /**
@@ -137,7 +140,7 @@ class Wechatpay {
      * @returns {PromiseLike} - The `AxiosPromise`
      */
     patch: async function(...arg) {
-      return Wechatpay.client.patch(Wechatpay.pathname(this.entities), ...arg)
+      return that.client.patch(that.pathname(this.entities), ...arg)
     },
 
     /**
@@ -146,7 +149,7 @@ class Wechatpay {
      * @returns {PromiseLike} - The `AxiosPromise`
      */
     delete: async function(...arg) {
-      return Wechatpay.client.delete(Wechatpay.pathname(this.entities), ...arg)
+      return that.client.delete(that.pathname(this.entities), ...arg)
     },
   } }
 
@@ -166,9 +169,9 @@ class Wechatpay {
       }
       if (!(property in target)) {
         /*eslint-disable-next-line*/
-        target[property] = new Proxy({...Wechatpay.container}, Wechatpay.handler)
+        target[property] = new Proxy({...this.container}, this.handler)
         if (`entities` in target) {
-          target[property].entities = [...target.entities, Wechatpay.normalize(property)]
+          target[property].entities = [...target.entities, this.normalize(property)]
         }
       }
 
@@ -184,15 +187,12 @@ class Wechatpay {
    * @returns {Proxy} - The magic APIv3 container
    */
   constructor(wxpayConfig = {}, axiosConfig = {baseURL: 'https://api.mch.weixin.qq.com'}) {
-    Wechatpay.client = Wechatpay.client || interceptor(axios.create(axiosConfig), wxpayConfig)
+    this.constructor.client = this.constructor.client || interceptor(axios.create(axiosConfig), wxpayConfig)
 
     /*eslint-disable-next-line*/
-    return new Proxy({...Wechatpay.container}, Wechatpay.handler)
+    return new Proxy({...this.constructor.container}, this.constructor.handler)
   }
 }
 
-/*eslint-disable-next-line*/
-const CLIENT = Symbol('CLIENT')
-
 module.exports = Wechatpay
 module.exports.default = Wechatpay
diff --git a/tests/lib/formatter.test.js b/tests/lib/formatter.test.js
index f151ab7..94d2927 100644
--- a/tests/lib/formatter.test.js
+++ b/tests/lib/formatter.test.js
@@ -219,4 +219,48 @@ describe('lib/formatter', () => {
       fmt.response(9,8).substr(-2).should.equal(`\n\n`)
     })
   })
+
+  describe('Formatter::joinedByLineFeed', () => {
+    it('method `joinedByLineFeed` should be static', () => {
+      should(fmt.joinedByLineFeed).be.a.Function()
+      should((new fmt).joinedByLineFeed).is.Undefined()
+    })
+
+    it('method `joinedByLineFeed` should returns a string which is end with LF(ASCII 10)', () => {
+      fmt.joinedByLineFeed('').should.be.a.String().endWith(`\n`)
+      fmt.joinedByLineFeed('').substr(-1).charCodeAt().should.equal(10)
+    })
+
+    it('method `joinedByLineFeed(a,b,c,d,e,f,g)` should returns a string, and filled as `aLFbLFcLFdLFeLFfLFgLF`', () => {
+      fmt.joinedByLineFeed('a', 'b', 'c', 'd', 'e', 'f', 'g').should.be.a.String()
+        /*eslint-disable-next-line quotes*/
+        .equal(`a\nb\nc\nd\ne\nf\ng\n`)
+        .and.startWith('a')
+        .and.endWith(`\n`)
+    })
+  })
+
+  describe('Formatter::ksort', () => {
+    it('method `ksort` should be static', () => {
+      should(fmt.ksort).be.a.Function()
+      should((new fmt).ksort).is.Undefined()
+    })
+
+    it('method `ksort({b: 1, a: 0})` should returns an object and deepEqual to {a: 0, b: 1}', () => {
+      fmt.ksort({b: 1, a: 0}).should.be.an.instanceOf(Object).and.have.properties([`a`, `b`])
+      fmt.ksort({b: 1, a: 0}).should.deepEqual({a: 0, b: 1})
+    })
+  })
+
+  describe('Formatter::queryStringLike', () => {
+    it('method `queryStringLike` should be static', () => {
+      should(fmt.queryStringLike).be.a.Function()
+      should((new fmt).queryStringLike).is.Undefined()
+    })
+
+    it('method `queryStringLike({appid: 3, mchid: 2, openid: \'\', sign: 0})` should returns a string and equal to `appid=3&mchid=2`', () => {
+      fmt.queryStringLike({appid: 3, mchid: 2, openid: '', sign: 0}).should.be.a.String()
+      fmt.queryStringLike({appid: 3, mchid: 2, openid: '', sign: 0}).should.equal(`appid=3&mchid=2`)
+    })
+  })
 })
diff --git a/tests/lib/rsa.test.js b/tests/lib/rsa.test.js
index 6e6b85f..7ef5650 100644
--- a/tests/lib/rsa.test.js
+++ b/tests/lib/rsa.test.js
@@ -20,8 +20,6 @@ describe('lib/rsa', () => {
         rsa.encrypt()
       }).throw(TypeError, {
         code: 'ERR_INVALID_ARG_TYPE',
-        message: 'The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received undefined',
-        stack: /at Function\.from \(buffer\.js/
       })
     })
 
@@ -30,8 +28,6 @@ describe('lib/rsa', () => {
         rsa.encrypt('')
       }).throw(TypeError, {
         code: 'ERR_INVALID_ARG_TYPE',
-        message: 'The "key" argument must be of type string or an instance of Buffer, TypedArray, DataView, or KeyObject. Received an instance of Object',
-        stack: /at prepareAsymmetricKey \(internal\/crypto\/keys\.js/
       })
     })
 
@@ -72,8 +68,6 @@ describe('lib/rsa', () => {
         rsa.decrypt()
       }).throw(TypeError, {
         code: 'ERR_INVALID_ARG_TYPE',
-        message: 'The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received undefined',
-        stack: /at Function\.from \(buffer\.js/
       })
     })
 
@@ -82,8 +76,6 @@ describe('lib/rsa', () => {
         rsa.decrypt('')
       }).throw(TypeError, {
         code: 'ERR_INVALID_ARG_TYPE',
-        message: 'The "key" argument must be of type string or an instance of Buffer, TypedArray, DataView, or KeyObject. Received an instance of Object',
-        stack: /at prepareAsymmetricKey \(internal\/crypto\/keys\.js/
       })
     })