Question

当我通过npm通过AWS模拟在Javascript测试中执行Jest时，将是失败。因为我使用单例课程。

像这里的区别。

“ module.exports = Users;”或“ module.exports = new Users（）;”

我想AWS模拟不适用于单例类。

在那个原因下，我应该怎么解决这个问题？

'use strick';

var aws = require('aws-sdk')
aws.config.update({region:'ap-northeast-1'})

class Users {

    constructor() {
        this.table = 'Users'
        this.dynamodb = new aws.DynamoDB()
    }

    getData(email) {
        let params = {
            TableName: this.table,
            Key      : { 'email': {'S':email} }
        }

        return this.dynamodb.getItem(params).promise()
    }
}
// module.exports = Users // ← this will be success.
module.exports = new Users(); // ← this will be failure.

'use strict';

var aws = require('aws-sdk-mock'),
    users = require('./user'),
    chai = require('chai'),
    path = require('path'),
    should = chai.should(),
    input = 'test@gmail.com',
    usersObj;

aws.setSDK(path.resolve('node_modules/aws-sdk'));

describe('All Tests', function () {
    // this.timeout(0);
    beforeEach(function () {
        aws.mock('DynamoDB', 'getItem', function (params, callback) {
            callback(null, {Item: {email: params.Key.email.S}});
        });

        // usersObj = new users(); ← this will be success.
        usersObj = users; // ← this will be failure.
    });

    it('getData', function (done) {
        usersObj.getData(input).then(function (res) {

            console.log(res);

            res.Item.email.should.equal(input);
            done();
        });
    });
});

Answer 1

此行：

module.exports = new Users();

...表示在代码运行后将立即创建一个Users对象，并且在user.js为required时它将立即运行。

此行：

users = require('./user')

...位于测试文件的顶部和以下行：

aws.mock('DynamoDB', 'getItem', function (params, callback) {
  callback(null, {Item: {email: params.Key.email.S}});
});

...在beforeEach中...

...这意味着user.js是required，并在创建模拟之前运行...导致测试失败。

如果您要导出Users的实例，则只需要确保直到之后，才require测试中的user.js文件您已经设置了模拟：

var aws = require('aws-sdk-mock'),
  chai = require('chai'),
  path = require('path'),
  input = 'test@gmail.com',
  usersObj;
chai.should()

aws.setSDK(path.resolve('node_modules/aws-sdk'));

describe('All Tests', function () {
  beforeEach(function () {
    aws.mock('DynamoDB', 'getItem', function (params, callback) {
      callback(null, { Item: { email: params.Key.email.S } });
    });  // <= set up the mock first...

    usersObj = require('./user');  // <= ...then require user.js
  });

  it('getData', function (done) {
    usersObj.getData(input).then(function (res) {
      res.Item.email.should.equal(input);  // Success!
      done();
    });
  });
});

Answer 2

我也可以解决这个问题。

'use strict';

var aws = require('aws-sdk-mock'),
    users = require('./user'),
    chai = require('chai'),
    path = require('path'),
    should = chai.should(),
    input = 'test@gmail.com',
    usersObj;

const awsObject = require('aws-sdk');

aws.setSDK(path.resolve('node_modules/aws-sdk'));

describe('All Tests', function () {
    // this.timeout(0);
    beforeEach(function () {
        aws.mock('DynamoDB', 'getItem', function (params, callback) {
            callback(null, {Item: {email: params.Key.email.S}});
        });

        // it will be resolve problem by creating new AWS instance.
        users.dynamodb = new awsObject.DynamoDB();
    });

    it('getData', function (done) {
        users.getData(input).then(function (res) {

            console.log(res);

            res.Item.email.should.equal(input);
            done();
        });
    });
});

Answer 3

您必须在类构造函数内调用aws客户端

class MyClass {
  constructor(){
    this.dynamodb = new DynamoDB.DocumentClient({ region: "us-west-2" });
  }
...

在测试文件中，必须在调用de AWSMock之后立即创建类的新实例。示例：

it('Should save on dinamoDB with param atributes void()', async () => {
  AWSMock.mock('DynamoDB.DocumentClient', 'update', function (params, callback){
    callback(null, { Attributes: { currentValue: 1 } } );
  });
  AWSMock.mock('DynamoDB.DocumentClient', 'put', function (params, callback){
    callback(null, true);
  });

  const myClass = new MyClass();
...

如何使用单例类解决AWS模拟测试

3 个答案: