ReferenceError: You are trying to `import` a file after the Jest environment has been torn down
Solution 1
OK, found a solution.
Should use jest.useFakeTimers()
Note: Put the code above just after import
section in your test file.
Solution 2
jest.useFakeTimers()
With above it's extremely important to understand this
jest.useFakeTimers() mocks out setTimeout and other timer functions with mock functions.
If running multiple tests inside of one file or describe block, jest.useFakeTimers(); can be called before each test manually or with a setup function such as beforeEach.
Not doing so will result in the internal usage counter not being reset.
Solution 3
I would like to contribute to the answer.
Well let's see the error message
ReferenceError: You are trying to 'import' a file after the Jest environment has been torn down.
Torn down means: Jest already finished running and some part of your code is trying to execute after jest torn down or exited your test. This is pretty common on Javascript due to its asynchronous nature.
Sometimes it happens after a promise callback getting executed for example:
import { someProcess} from 'a-library'
task.job().then(result => {
someProcess(result)
})
In the example above the code imports someProcess
from a-library
If the method job
from the task
object takes longer than the jest execution its callback (then() invocation) will run outside jest because jest has continued. Therefore when someProcess
gets executed it will be loaded from a-library
so jest will complain that you are trying to load a library after jest has been torn.
The answer marked as the solution is partially right because calling jest.useFakeTimers()
will prevent your code to wait the n seconds you supposed to wait calling setTime or similars making your code artificially sincrhonoyus
Making your test await
those method calls would help you understand better your code.
The code that worked for me was
describe("Some test set " , ()=>{
let heavyWorkinService = library.workingService();
// We are marking the test function call as async
test(("Name of the test"), async ()=>{
// we are awaiting heavyWorkingService to done its job
await hevyWorkingService("some data")
})
})
In my real scenario my code was getting data from firebase, because am not using mocks for this test it was trying to import firebase after .get() data read returned so marking the test as async
and calling the method with await
keyword solved my problem
Of course there are a lot of ways to dealing with this error, just wanted you to know the true reason behind this error so you can work in the right solution for your tests!
Solution 4
I am using @testing-library/react-native
, so what I did is to cleanup
in the setup file.
// jest.setup.js
import { cleanup } from '@testing-library/react-native';
afterEach(cleanup);
Solution 5
Add "testEnvironment": "jsdom"
into jest
key in package.json or jest.config.js
"jest": {
"testEnvironment": "jsdom",
"preset": "react-native",
...
taken from: https://stackoverflow.com/a/64567257/728287
nrion
I am a Software Engineering student from the Philippines, currently exploring the vast canvas of web development with Javascript, Node.js, React and Redux! So that's my main thing right now. Lately, I've been into learning GraphQL and Apollo. I'm also a freelancer, currently hired by 3 remote companies. I have also been joining city-wide coding tournaments to assess my coding capabilities and was recently granted a Proxor 3 rating via one of its assessments.
Updated on January 28, 2022Comments
-
nrion over 2 years
I have a component that makes use of
Animated
component from react native. I started writing a test case to simulateonPress
of a component, which calls a function that hasAnimated.timing
in it, andsetState
.running
jest
works fine, but the tests never stops running, and one unrelated test case that I've written before never seem to pass now (which passed before).running
jest --watch
, I get this error:ReferenceError: You are trying to `import` a file after the Jest environment has been torn down. at Function.bezier (node_modules/react-native/Libraries/Animated/src/Easing.js:113:21) at ease (node_modules/react-native/Libraries/Animated/src/Easing.js:34:24) at TimingAnimation._easing (node_modules/react-native/Libraries/Animated/src/Easing.js:133:18) at TimingAnimation.onUpdate (node_modules/react-native/Libraries/Animated/src/animations/TimingAnimation.js:107:45) RUNS src/__tests__/SlideDownMenu.test.js /home/nrion/Desktop/mobile-ui/PriceInsight_app/node_modules/react-native/Libraries/Animated/src/Easing.js:114 return _bezier(x1, y1, x2, y2); ^ TypeError: _bezier is not a function at Function.bezier (/home/nrion/Desktop/mobile-ui/PriceInsight_app/node_modules/react-native/Libraries/Animated/src/Easing.js:224:12) at ease (/home/nrion/Desktop/mobile-ui/PriceInsight_app/node_modules/react-native/Libraries/Animated/src/Easing.js:94:21) at TimingAnimation._easing (/home/nrion/Desktop/mobile-ui/PriceInsight_app/node_modules/react-native/Libraries/Animated/src/Easing.js:255:16) at TimingAnimation.onUpdate (/home/nrion/Desktop/mobile-ui/PriceInsight_app/node_modules/react-native/Libraries/Animated/src/animations/TimingAnimation.js:138:14) at ontimeout (timers.js:386:11) at tryOnTimeout (timers.js:250:5) at Timer.listOnTimeout (timers.js:214:5)
Link to repl
https://repl.it/repls/PartialGrimyMetadata
Environment:
- OS: Linux 4.14
- Node: 6.14.2
- Yarn: 1.7.0
- npm: 3.10.10
- Watchman: Not Found
- Xcode: N/A
- Android Studio: Not Found