使用 jest 使用 aws-sdk-mock 模拟 aws-sdk 承诺答案

【问题标题】：Mocking aws-sdk promises with aws-sdk-mock using jest使用 jest 使用 aws-sdk-mock 模拟 aws-sdk 承诺
【发布时间】：2019-05-17 20:07:52
【问题描述】：

你能看看下面的代码并告诉我它有什么问题吗？代码在 5 秒后超时，但根据官方描述，我希望它可以正常运行。

有没有人看到根本上的错误？

import * as AWS from "aws-sdk-mock";
import * as _AWS from "aws-sdk"; 

beforeAll(async (done) => {
  //get requires env vars
 });

describe("the module", () => {

  it("should read from the database", async () => {
    AWS.mock('DynamoDB.DocumentClient', 'get', (error, callback) => { callback(null, "got it")});
    expect(await (new _AWS.DynamoDB.DocumentClient()).get({TableName:"", Key: {pk: "foo", sk: "bar"}}).promise()).toBe("got it");
  });
});

afterAll(() => {
  AWS.restore();
});

【问题讨论】：

可能还有其他问题，但上面代码中的超时是由于在beforeAll中使用了done而从未调用它

标签： typescript jestjs aws-sdk aws-sdk-mock

【解决方案1】：

我终于找到了可行的变体：

import * as AWSMock from "aws-sdk-mock";
import * as AWS from "aws-sdk"; 
import { GetItemInput } from "aws-sdk/clients/dynamodb";

beforeAll(async (done) => {
  //get requires env vars
  done();
 });

describe("the module", () => {

  it("should mock getItem from DynamoDB", async () => {

    AWSMock.setSDKInstance(AWS);
    AWSMock.mock('DynamoDB', 'getItem', (params: GetItemInput, callback: Function) => {
      console.log('DynamoDB', 'getItem', 'mock called');
      callback(null, {pk: "foo", sk: "bar"});
    })

    let input:GetItemInput = { TableName: '', Key: {} };
    const dynamodb = new AWS.DynamoDB({apiVersion: '2012-08-10'});
    expect(await dynamodb.getItem(input).promise()).toStrictEqual( { pk: 'foo', sk: 'bar' });

    AWSMock.restore('DynamoDB');
  });

  it("should mock reading from DocumentClient", async () => {

    AWSMock.setSDKInstance(AWS);
    AWSMock.mock('DynamoDB.DocumentClient', 'get', (params: GetItemInput, callback: Function) => {
      console.log('DynamoDB.DocumentClient', 'get', 'mock called');
      callback(null, {pk: "foo", sk: "bar"});
    })

    let input:GetItemInput = { TableName: '', Key: {} };
    const client = new AWS.DynamoDB.DocumentClient({apiVersion: '2012-08-10'});
    expect(await client.get(input).promise()).toStrictEqual( { pk: 'foo', sk: 'bar' });

    AWSMock.restore('DynamoDB.DocumentClient');
  });
});

【讨论】：