Add window to jest setup

[timomeh]

Summary

window exists in the React Native runtime, but not inside the test environment. Many libraries use typeof window === 'undefined' to check if code is running in SSR. Because of the difference in the real environment and test environment, tests can behave different than the real app, which is an unwanted behavior.

Background

I'm using https://github.com/tannerlinsley/react-query in my React Native Project, which works really well. When writing tests, they wouldn't work: jest started and then seemingly did nothing. While debugging I noticed the render was stuck in an infinite loop. Then I noticed the following line inside react-query:

const isServer = typeof window === 'undefined'

I didn't know that the React Native runtime has a global window, and thought it's a bug inside react-query. But it does have a window, which is not defined inside the test environment.

The infinite loop was caused by react-query thinking it is running on the server, which doesn't fetch any data. If the react-query hook mounts, it re-executes because then it should be mounted inside the client. But isServer was still true. This repeats forever.

Changelog

[General] [Fixed] - Fix window not existing in jest setup

Test Plan

Are there tests to check if the test environment is setup correctly? 🤔

[analysis-bot]

RNTester (Android/hermes/arm64-v8a): 3289088 bytes
RNTester (Android/hermes/armeabi-v7a): 3129344 bytes
RNTester (Android/hermes/x86): 3461120 bytes
RNTester (Android/hermes/x86_64): 3424256 bytes
RNTester (Android/jsc/arm64-v8a): 4446208 bytes
RNTester (Android/jsc/armeabi-v7a): 4268032 bytes
RNTester (Android/jsc/x86): 4358144 bytes
RNTester (Android/jsc/x86_64): 4644864 bytes

[analysis-bot]

RNTester.app (iOS): 10657792 bytes

[charlesbdudley]

Thanks for this @timomeh, do you mind rebasing to get these tests to pass and we'll import for review?

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: f536f82

[timomeh]

@charlesbdudley Done! The test_ios_unit_hermes check is failing, but it also fails on the main branch.

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	9,241,399	+0
android	hermes	armeabi-v7a	8,753,218	+0
android	hermes	x86	9,684,388	+0
android	hermes	x86_64	9,652,601	+0
android	jsc	arm64-v8a	10,877,532	+0
android	jsc	armeabi-v7a	9,780,623	+0
android	jsc	x86	10,915,934	+0
android	jsc	x86_64	11,525,647	+0

Base commit: 3560753

[facebook-github-bot]

@charlesbdudley has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[facebook-github-bot]

@charlesbdudley merged this pull request in bc1c533.