Splitting this off from #10. @hammer would like 100% test coverage (nice round number). We're currently at zero.

Jest is the standard choice for any sort of unit test. React Testing Library is also the standard choice for testing React components and their interactions, though I'm open to alternatives here. Stubbing out Tauri interactions may be an issue.

End-to-end testing is also an interesting question but probably overkill for now. Playwright and Storybook are the tools I know about in that space.