correct some mistakes for global variable

test/album.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 describe('测试获取歌手专辑列表是否正常', () => {
   it('数据的 code 应该为200', done => {

test/comment.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 describe('测试获取评论是否正常', () => {
   it('数据的 code 应该为200', done => {

test/login.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 console.log("注意: 测试登录需在 test/login.test.js 中填写账号密码!!!");
 

test/lyric.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 describe("测试获取歌词是否正常", () => {
   it("数据应该有 lrc 字段", done => {

test/music_url.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 describe("测试获取歌曲是否正常", () => {
   it("歌曲的 url 不应该为空", done => {

test/search.test.js

@@ -1,6 +1,6 @@
 const assert = require('assert')
 const request = require('request')
-host = global.host || 'http://localhost:3000'
+const host = global.host || 'http://localhost:3000'
 
 describe('测试搜索是否正常', () => {
   it('获取到的数据的 name 应该和搜索关键词一致', done => {