Testing

We should have a proper testing strategy. There's probably a few things we should do:
- [ ] test stores in Node
- [ ] test component lifecycles
- [ ] assert rendering works for views

Possibly bonus:
- [ ] test service workers with [sw-test-env](https://github.com/popeindustries/sw-test-env)
- [ ] snapshot testing components

We might need to write some packages to wrap this up nicely.

Start by breaking the proposed testing strategy into separate scopes: Node stores, component lifecycles, view rendering, service workers, and snapshot testing. Identify the relevant stores, components, views, and existing test entry points before choosing a package approach; the work is done when the agreed checklist has reliable coverage and its test setup is documented.

Written by the indexing model from the issue text.