improve a test case (#6629)

1. do not need to create a new server, use the reconfigureServer tool
3. use async await

Co-authored-by: Gordon Sun <gordon.sun@pipe17.com>

spec/EnableExpressErrorHandler.spec.js

@@ -1,54 +1,33 @@
-const ParseServer = require('../lib/index');
-const express = require('express');
 const request = require('../lib/request');
 
 describe('Enable express error handler', () => {
-  it('should call the default handler in case of error, like updating a non existing object', done => {
-    const serverUrl = 'http://localhost:12667/parse';
-    const appId = 'anOtherTestApp';
-    const masterKey = 'anOtherTestMasterKey';
-    let server;
-
-    const parseServer = ParseServer.ParseServer(
+  it('should call the default handler in case of error, like updating a non existing object', async (done) => {
+    const parseServer = await reconfigureServer(
       Object.assign({}, defaultConfiguration, {
-        appId: appId,
-        masterKey: masterKey,
-        serverURL: serverUrl,
         enableExpressErrorHandler: true,
-        serverStartComplete: () => {
-          expect(Parse.applicationId).toEqual('anOtherTestApp');
-          const app = express();
-          app.use('/parse', parseServer);
-
-          server = app.listen(12667);
-
-          app.use(function(err, req, res, next) {
-            expect(err.message).toBe('Object not found.');
-            next(err);
-          });
-
-          request({
-            method: 'PUT',
-            url: serverUrl + '/classes/AnyClass/nonExistingId',
-            headers: {
-              'X-Parse-Application-Id': appId,
-              'X-Parse-Master-Key': masterKey,
-              'Content-Type': 'application/json',
-            },
-            body: { someField: 'blablabla' },
-          })
-            .then(() => {
-              fail('Should throw error');
-            })
-            .catch(response => {
-              expect(response).toBeDefined();
-              expect(response.status).toEqual(500);
-            })
-            .then(() => {
-              server.close(done);
-            });
-        },
       })
     );
+    parseServer.app.use(function (err, req, res, next) {
+      expect(err.message).toBe('Object not found.');
+      next(err);
+    });
+
+    try {
+      await request({
+        method: 'PUT',
+        url: defaultConfiguration.serverURL + '/classes/AnyClass/nonExistingId',
+        headers: {
+          'X-Parse-Application-Id': defaultConfiguration.appId,
+          'X-Parse-Master-Key': defaultConfiguration.masterKey,
+          'Content-Type': 'application/json',
+        },
+        body: { someField: 'blablabla' },
+      });
+      fail('Should throw error');
+    } catch (response) {
+      expect(response).toBeDefined();
+      expect(response.status).toEqual(500);
+      parseServer.server.close(done);
+    }
   });
 });