Jest return mocked value when S3.getObject function is called

Question

I'm totally new to Jest and typescript. my 2nd test case to be honest. I want in my jest test - when s3.getObject is called in the actual class, it should return the mocked value.

my handler code:

var aws = require("aws-sdk");
var s3 = new aws.S3({apiVersion: '2006-03-01'});

exports.handler = async function (event, context, callback) {
    const bucket = 'event.s3.bucket.name';
    const filename = 'fileName'; 
    const inputBucketParams = {
        Bucket: bucket,
        Key: filename,
    }; 
    let result;
    
        try {
            **//I want the result to be the mocked value in my test case.**
            result = await s3.getObject(inputBucketParams).promise();
            const fileContent = getFileContents(result.Body.toString("utf-8"));

my test case:

import {getFileContent} from "../../utils/FileContent";
import anything = jasmine.anything;


const lambdaHandler = require('../lambda/myLambda');
const AWSMock = require('aws-sdk-mock');
const AWS = require("aws-sdk");

describe('Test getS3Object', () => {
    beforeEach(() => AWSMock.setSDKInstance(AWS));
})


let s3Object = {
    "bucket": {
    },
    "object": {
        
    }
};


let event = {Records: [
        {
            s3: s3Object --> from above.
        }
    ]
}

var aws = require("aws-sdk");
var s3 = new aws.S3({apiVersion: '2006-03-01'});

describe('my handler test', async function () {
    const s3GetObject = AWSMock.mock('S3', 'getObject', getFileContent('fileName.csv'));
    const s3mock = jest.fn();
    const getObjectMock = jest.fn(() => getFileContent('fileName.csv'));
    const params = {
        Bucket: 'bucketName',
        Key: 'filename'
    }
    var returnValue = s3mock.mockReturnValue({
        Body: getFileContent('fileName.csv')
    });

    test('s3 getObject response mock', async () => {
        //jest.spyOn(s3, "getObject")
        const getObjectMockValue = s3.spyOn('S3', 'getObject').mockReturnValue({
                Body: getFileContent('fileName.csv')
        })

    // my handler is called from this, and when it get to s3.getObject, it fails.
        const handlerResponse = await lambdaHandler.handler(event, anything(), anything());
    });
});

I want in my jest test - when s3.getObject is called in the actual class, it should return the mocked value.

Jest return mocked value when S3.getObject function is called

0 Answers0