节点：无法模拟 aws-sdk 方法

Question

我已经尝试了很多我在互联网上找到的关于模拟 aws-sdk 服务的方法，但没有一个对我有用，我什至尝试了模块 aws-sdk-mock，但这不起作用，我认为这是因为我没有在函数处理程序中使用aws-sdk。

我使用jest 作为我的测试运行器和断言，所以我现在的代码是这样的：

test.js

const aws = require('aws-sdk-mock');
const Admin = require('./../../../serverless/entities/Admin');

describe('Entity - Admin test', () => {
  jest.spyOn(aws.CognitoIdentityServiceProvider.prototype, 'listUsersInGroup', () => {
    return {
      promise: Promise.resolve({ foo: 'bar' })
    };
  });

  const data = Admin.getListOfUsers();

  console.log(data);
});

Admin.js

/**
 * Admin entity class
 * This class should help managing all super user actions that are required for the sportstracker's application
 * Amazon services used by this entity:
 *  - Cognito (User Pool)
 * Required IAM Policy actions:
 *  - cognito-idp:ListUsersInGroup
 *  - cognito-idp:ListUsers
 *  - cognito-idp:AdminCreateUser
 *  - cognito-idp:AdminDeleteUser
 *  - cognito-idp:AdminGetUser
 *  - cognito-idp:AdminListGroupsForUser
 *  - cognito-idp:AdminUpdateUserAttributes
 *  - cognito-idp:AdminRemoveUserFromGroup
 */

const aws = require('aws-sdk');
const User = require('./../lib/User');
const cognito = new aws.CognitoIdentityServiceProvider();
const UserPoolId = process.env['COGNITO_USER_POOL_ID'];

const rolesMap = {
  admin: 'SuperUser',
  member: 'Member'
};

/**
 * @typedef UsersList
 * @property {Array<UserObject>} members - The list of members
 * @property {Array<UserObject>} admins - The list of admins
 */

class Admin {
  /**
   * Gets a list of users for both admin and members.
   * This executes 2 methods for aws.cognito [admin, member]
   * @returns {Promise<UsersList>} - The object containing the list of members and admins
   */
  static async getListOfUsers () {
    const operations = [
      cognito.listUsersInGroup({ UserPoolId, GroupName: rolesMap.admin }).promise(),
      cognito.listUsersInGroup({ UserPoolId, GroupName: rolesMap.member }).promise()
    ];

    const results = await Promise.all(operations);

    return {
      admins: results[0].Users.map(user => User.mapUserData(user)),
      members: results[1].Users.map(user => User.mapUserData(user))
    };
  }

  ...
}

module.exports = Admin;

我得到的这段代码的错误是：

TypeError: Cannot read property 'prototype' of undefined

这是因为 sdk 中所有服务的原型在调用构造函数之前都没有定义方法，我明白为什么他们创建了一个像 aws-sdk-mock 这样的模块，但即使那个模块也没有帮助我，所以我该怎么做在非函数 lambda 处理程序中模拟 aws 服务的正确方法？

Answer 1

要模拟jest 中的第三方包，您可以在node_modules 的同一级别中创建一个__mocks__ 目录，该目录将包含您的模拟函数。

例如，

.
├── README.md
├── __mocks__
    └── aws-sdk.js
├── jest.config.js
├── node_modules
├── package.json
├── src
└── yarn.lock

您的aws-sdk.js 模拟文件可以包含以下内容：

module.exports.CognitoIdentityServiceProvider = jest.fn(() => ({
    listUsersInGroup: mockListUsersInGroup,
}))

const mockListUsersInGroup = jest.fn((params) => ({
    // You can replace the resolved value.
    promise: () => Promise.resolve({}),
}))

Answer 2

这个适合我

const AWS = require('aws-sdk');
jest.mock('aws-sdk');
    
AWS.CognitoIdentityServiceProvider.prototype.listUsers = jest.fn().mockReturnValue({
      promise: jest.fn().mockResolvedValue({})
    });