chore: add missing tests for vscode features

[lcottercertinia]

Is your feature request related to a problem?

There is missing test coverage around the vscode parts of the app, mainly launching the log-viewer page. it would be great to increase case coverage so we can be more confident we do not break things as we add more features to the vscode extension side.

Describe the solution you'd like

• Add missing tests + test harness
• Get them working in CI

More detail can be found here https://code.visualstudio.com/updates/v1_36#_splitting-vscode-package-into-typesvscode-and-vscodetest

https://code.visualstudio.com/api/working-with-extensions/testing-extension