ReferenceError: You are trying to `import` a file after the Jest environment has been torn down

Question

I have a component that makes use of Animated component from react native. I started writing a test case to simulate onPress of a component, which calls a function that has Animated.timing in it, and setState.

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

Answer 1

OK, found a solution.

Should use jest.useFakeTimers()

Note: Put the code above just after import section in your test file.

Answer 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.

Answer 3

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