Review https://dev.arvados.org/projects/arvados/wiki/Hacking_Workbench2 to get a better understanding of how WB2 is structured.

Reducers

Reducers are responsible for transitioning between states. These are straight forward to test. Start with an initial state, call the reducer with an action, and evaluate the resulting state.

Action creators and services

These are the components that invoke actions to change state and interact with outside resources (Axios, localstorage, etc). Need more research to figure out how to test these properly. Do we use the actual store, or mock it? Do we have to mock the entire service repository?

React UI Components

React components only rely on their connected props/state, which make them relatively easy to test using something like Enzyme. Consider snapshot testing for components that don't change often.

Resources: https://redux.js.org/recipes/writing-tests, https://willowtreeapps.com/ideas/best-practices-for-unit-testing-with-a-react-redux-approach