I see the answer here Mocking aws-sdk S3#putObject instance method using jest, but it's not working as-is and it's not explained at all so I don't know what's going on.

I have a function:

const AWS = require('aws-sdk');
const s3 = new AWS.S3();
exports.saveImageToS3 = async (params) => { 
    try {
        const s3resp = await s3.putObject(params).promise();
        /* Happy path response looks like this:
                    data = {
                        ETag: "\"6805f2cfc46c0f04559748bb039d69ae\"", 
                        VersionId: "psM2sYY4.o1501dSx8wMvnkOzSBB.V4a" // version optional
                    }*/
        if (s3resp.hasOwnProperty('ETag')) { // expected successful response            
            return { success: true, key: params.Key }  // returning key of item if we have reason to think this was successful.
        } else {
            console.warn("Unexpected s3 response format: ", s3resp)
            return s3resp;
        }

    } catch (err) {
        throw err;
    }
}

I'd like to test if it works.

I do not understand how to mock the s3.putObject function.

I have tried:

describe('FUNCTION: saveImageToS3', () => {
    const mockedPutObject = jest.fn();
    jest.mock('aws-sdk', () => {
        return class S3 {
            putObject(params, cb) {
                console.log("Mocked putObject function");
                mockedPutObject(params, cb);
            }
        }
    });

    test('returns success object with correct key value', async () => {
        await expect(await utils.saveImageToS3(params)).toEqual({ success: true, key: `original/testCamId/testCamId___2022-04-06T06-30-59Z.jpg` })
    })
})

per the above-linked answer, but the test fails (times out, actually) and the output "Mocked putObject function" never is written to the console, telling me the mocked aws-sdk isn't being used...