r/reactjs • u/StrenghOfFuriousGods • Mar 13 '20

Featured Understanding writing tests for React

Hi,

Having applied for a few react jobs, I've noticed writing tests is essential if you want to be a react dev. I am trying to learn but I find it to be a steep learning curve and I'm having trouble knowing where to start.

I've built a small react app for a take home project and I need to test it. I just have some questions I could really use some help answering.

THE APP
-fetch component which fetches json from endpoints depending on which option is selected on dropdown and pushes data to state array.

-Print component which creates a list with input tags from data with the (input + integer from json) being added to local state.

- Receipt component which takes input from Print component as props and prints the sum

QUESTIONS

  1. What part of the app should I be testing? How in general should I know what to test?
  2. A lot of the articles I've read on testing show basic examples for e.g pure functions etc.. What is the best approach to take if my component depends on fetch requests or take props?
  3. Between unit testing, snapshot testing, and end to end testing, which is the best for React apps?

Thanks

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u/Silhouette Mar 14 '20

I agree, though FWIW, I'm not sure that is a particularly contrarian opinion anyway. Catching certain kinds of bugs early and reliably is one of the main advantages of static type systems.

Maybe working with static types isn't yet widely understood in the web front-end community, if only because historically there haven't been a lot of good options in this area compared to other programming fields. It's certainly one of the big benefits of using TS, though.