Set up jest for component testing

[TvrtkoM]

Write a couple of tests for some components of small to medium complexity, and come up with a plan for refactoring other components so they're more easy to test

[TvrtkoM]

Investigated so far:

Jest (since we already use it for unit testing)

• runs in nodejs
• node related errors when running e.g. ReferneceError: TextDecoder is not defined
• couldn't get it to work
• configuration feels like hit and miss

Main issues is in uint8arrays dependency that seem to originate from polkadotjs dependencies / sdk and it is related to ipfs-http-client

.../.../zeitgeist/ui/node_modules/multihashes/node_modules/uint8arrays/esm/src/to-string.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){import bases from './util/bases.js';

Cypress

• runs in browser so there were no nodejs related issues
• configuration was running smoothly
• disadvantage is having to deal with cypress promises instead of async / await code, but it seems there are some libs that can help with that
• another disadvantage is not being able to mock modules, so it's not possible to mock hooks, but instead requests can be intercepted with cy.intercept
• should investigate usage of cypress with visual regression tools like percy (https://percy.io/) or happo (https://happo.io/)

[TvrtkoM]

Another library to consider is https://storybook.js.org/

[lsaether]

Look into replacing ipfs-http-client with something else / our own code since it continues to give us issues.