Add tests

[sheremet-va]

Currently, we only have unit tests for some of the functionality, but it would be nice to also have integration tests using Electron API to catch regressions: https://code.visualstudio.com/api/working-with-extensions/testing-extension

[MilanKovacic]

I can take this one.

[ffMathy]

Sorry, didn't see this issue. I already have a PR that works for this. See the referenced PR.

[MilanKovacic]

No problem, I will add a smoke end-to-end test instead.

[sheremet-va]

No problem, I will add a smoke end-to-end test instead.

Yeah, this issue is about integration/e2e tests for the extension to catch regressions earlier.

[sheremet-va]

I added a "needs test" label. Anyone who wants to help, can look through all issues with that label and write a test 😄