What's your approach to unit-testing React components in Kotlin/JS? I found this <https://github.com...

# javascript

[Piotr Krzemiński]

What's your approach to unit-testing React components in Kotlin/JS? I found this https://github.com/mysticfall/Kotlin-react-test but it's pretty new - I'm wondering if there are any well-established practices. My goal is to take a component that possibly uses other components under the hood, and both be able to test it by verifying that it calls underlying components correctly, and assert on complete DOM.

[Piotr Krzemiński]

In https://github.com/JetBrains/create-react-kotlin-app there's this note "Unit testing is currently not supported in this project. We're now working on the Jest Kotlin wrapper. Stay tuned!". It's been there for 4 years already! :(

[Piotr Krzemiński]

I also see no mention of unit testing in "Building Web Applications with React and Kotlin JS" hands on tutorial

[Piotr Krzemiński]

I've searched for a relevant ticket in YouTrack, but I don't see one, so I created this: [KT-49610] Allow unit-testing React components

[Piotr Krzemiński]

also proposing such change: https://github.com/JetBrains/create-react-kotlin-app/pull/493

[turansky]

https://github.com/JetBrains/kotlin-wrappers/issues

[Piotr Krzemiński]

thanks! in particular: https://github.com/JetBrains/kotlin-wrappers/issues/325

[Tim Lavers]

I'm trying to get this working:
https://github.com/JetBrains/kotlin-wrappers/tree/master/kotlin-react-dom-test-utils

So far I am not able to get a test running, will keep trying.

[turansky]

@Tim Lavers Test utils works fine.
Example

Important:
• Async JS test must return Promise<Unit>
◦ Multiplatform adapter - TestResult
• Simulate works
• dispatchEvent , which used in React docs - doesn’t work 😞

[turansky]

runReactTest will be available in next release 🙂

[Tim Lavers]

Thanks @turansky I am following the code in your Seskar repo. It's working. I was not even close to getting things going so thanks again.

[turansky]

runReactTest released in pre.480

[Edoardo Luppi]

I came around https://youtrack.jetbrains.com/issue/KT-49610/ just now trying to understand the testing situation. Seems like there is still no Jest wrapper for Kotlin, but will it work anyway if run on Mocha?
Just asking as Jest is the recommended test framework for React.

[turansky]

What is your test cases?

[Edoardo Luppi]

Oh I was just wondering how people are approaching unit testing for K/JS React apps.
Mostly wondering if there are limitations in the way components can be tested, compared to a pure CRA solution

[turansky]

compared to a pure CRA solution

Do you have examples?

[Edoardo Luppi]

Not really, not yet at least. I'm evaluating frameworks for VS Code webviews, and the choice is between
• Angular (which I have used for many years now)
• React (with TS)
• React (with K/JS)
The point is I don't want to find myself in a situation where I can't properly test the UI