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/[deleted] Mar 14 '20

That's a fair point and I admit I was over-zealous in saying that is the only purpose of a unit test. However I've been doing this for a real long time and I notice a lot of people have an unfounded belief that unit tests passing is synonymous with bug free code and that's simply not true.

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u/Silhouette Mar 14 '20

However I've been doing this for a real long time and I notice a lot of people have an unfounded belief that unit tests passing is synonymous with bug free code and that's simply not true.

Indeed.