Add robust unit tests

[imcaizheng]

True unit tests. No real download or upload or zipping.

[sharathkumaranbu]

Still two tests fail in my system and I am in the right branch and repo.

I am using Ubuntu 18.04. Also, please note that the folders are still being created inside the repo. It shouldn't happen as well.

The code repo should remain as is. No additional folders or files should be created.

[imcaizheng]

I can reproduce the errors only by setting WAIT_TIME to below ~200ms before running the tests.
I think the default WAIT_TIME should be sufficient for running the tests though I still don't know why it doesn't work for you. I reduce the total number of artifacts in test/common/testData.js so that the fetch-artifacts command could exit more quickly. Let me know if the new changes could help you run the tests without errors.

[sharathkumaranbu]

If I increase the timeout in my system, it works fine. We will try in the CI / CD pipeline.

[sharathkumaranbu]

All good now.