feat: update jest v20 to v24

[trivikr]

Issue #, if available:
N/A

Description of changes:
This PR updates jest from v20 to v24

Pending (to be done separately as this update is not delayed):

• Uncomment and fix test with localStorage (fixed in cbe89e2 thanks to @AllanFly120)
• Uncomment and fix test which requires NODE_TLS_REJECT_UNAUTHORIZED=0 in node-http-handler.spec.js (issue created at fix: node-http-handler tests which require NODE_TLS_REJECT_UNAUTHORIZED=0 #244)

All experimental commits can be viewed in fork https://github.com/trivikr/aws-sdk-js-v3/tree/jest-update

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[AllanZhengYP]

Just out of curiosity, is this code allowed in jest 24?

[trivikr]

jest.fn().mockReturnValue(value) is just a simple sugar function for jest.fn(() => value)
It's backward compatible, but was removed as it was failing pretest

[AllanZhengYP]

@trivikr Now the default testMatch of jest 24 includes ts file directly(https://jestjs.io/docs/en/configuration#testmatch-array-string). This means we cannot run test command under each sub package, because jest will fail testing the .ts files without setting the transpiler. We might also need to add jest config in each sub-package to make jest only run test on .js files

[trivikr]

@AllanFly120 I'll rename root file to jest.config.base.js and extend it in jest.config.js in packages/*
This way param testMatch will be removed when we move to ts-jest

[trivikr]

I'd experimented with adding jest.config.js in packages/* while experimenting with removing lerna run pretest in trivikr@13aea99

lerna run pretest will be removed when we move to ts-jest

[AllanZhengYP]

For the record of the off-line discussion on node-http-handler tests:

1. Jest introduces some changes since 21.X. The override of NODE_TLS_REJECT_UNAUTHORIZED in the unit test is not received by https.request. So the tests for https request failed because of self assigned certs. We have tried different approaches including calling resetModules() but they didn't help.

2. This situation can be fixed by ping the jest version specificly for this this package. But this require use to run jest test command individually in each packages. This approach make the testing very slow(because of lerna exec) and more importantly, we cannot get global coverage report.

3. Current step is to temporarily remove the https tests and open issue report to Jest repo. Hopefully they will get it fixed or provide a solution. Then we will add back these tests.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs and link to relevant comments in this thread.