javascript - 无法使用 jest 模拟 s3

问题描述

我想模拟 s3.listObjects.promise() 并返回一个模拟值。但是，我不能这样做。这是我的实际代码，然后是单元测试。

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

exports.handler = async (event,context,callback) => {
    console.log(`event is ${JSON.stringify(event)}`);

    const Bucket = event.s3Usage.Bucket;
    const Prefix = event.s3Usage.Prefix || "";

    let s3BucketSize = 0;
    console.log(`Bucket name is ${Bucket} and Prefix is ${Prefix}`);
    
    const s3 = new AWS.S3();
    try {
        const data = await s3.listObjects({ Bucket, Prefix }).promise();
        console.log(`Data is ${JSON.stringify(data)}`);
        if (data["Contents"].length > 1) {
            s3BucketSize = data["Contents"].filter(x => x.Size > 0).map(x => x.Size).reduce((x, y) => x + y);
            console.log(`Size of the folder is ${s3BucketSize} bytes.`);
        } else {
            console.log(`Size of the folder is 0 bytes.`);
        }
    } catch (err) {
        console.error(`Error is ${JSON.stringify(err)}`);
        callback(err)
    }

    return s3BucketSize;
}

以下是我的单元测试： -

const handler = require("../index").handler;
const { S3 } = require('aws-sdk');

jest.mock('aws-sdk');

const mockOutput = {
    "IsTruncated": false,
    "Marker": "",
    "Contents": [
        {
            "Key": "GodIsGreat.PNG",
            "LastModified": "2021-05-04T14:32:59.000Z",
            "ETag": "\"b45d6e6a40ab1c9ebf541093fe8959e6\"",
            "Size": 100,
            "StorageClass": "STANDARD",
            "Owner": {
                "ID": "98062a6ccbfb88d9b333868c14d5379ec23dab90210de79b2bfbd801e948ae0c"
            }
        },
        {
            "Key": "test/",
            "LastModified": "2021-03-02T08:09:37.000Z",
            "ETag": "\"d41d8cd98f00b204\"",
            "Size": 50,
            "StorageClass": "STANDARD",
            "Owner": {
                "ID": "98062a6ccbfb88d9b3338"
            }
        }
    ],
    "Name": "xx",
    "Prefix": "",
    "MaxKeys": 1000,
    "CommonPrefixes": []
};

const s3ListObjectsPromise = jest.fn().mockReturnValue({
    promise: jest.fn().mockResolvedValue(mockOutput)
});

S3.mockImplementation(() => ({
    listObjects: s3ListObjectsPromise
}));


const event = {
    s3Usage: {
        "Bucket": "xxx",
        "Prefix": ""
    }
};

describe("When the handler is invoked with an event", () => {
    // afterEach(jest.clearAllMocks);
    test("the correct response is returned", async () => {
        const res = await handler(event);
        console.log(`res value is ${res}`);
    });
});

当我运行测试时，我看到对 S3 对象的实际调用正在发生。如何避免这种情况？谢谢。

标签： javascriptnode.jsamazon-web-servicesunit-testingjestjs

javascript - 无法使用 jest 模拟 s3

问题描述

解决方案

推荐阅读