[chore] test refactor/cleanup

[bradtaniguchi]

Is your feature request related to a problem? Please describe.

When testing locally the suite relies on the built source code, which includes both the src+test+mappings and even sometimes some nested source (like dist/dist?)

Also, during testing there appears to be a number of warnings/errors and coverage flags. 100% coverage is often over-rated, but its worth looking into as a last step after cleaning up what is getting flagged.

Describe the solution you'd like

I can think of a few approaches:

• utilize babel + typescript + jest to allow jest to directly test the generated TS code. Means more tooling though (see here
• use ts-jest (see link above), but I've found startup times to be slow out of the box, might need tweaking
• stick with the current pattern, but clean up the compile step (for testing+production builds), might be done after chore: update dx #75