require.requireActual not returning the actual mock

[calclavia]

I create a simple test with Jest's default automatic mocking. I'm trying to test one of my app's modules, so I need to make sure the module I am testing is not mocked. However, using jest.unmock('../moduleName') did not seem to work.

I also tried using require.requireActual('../moduleName'), which also did not work.
https://facebook.github.io/jest/docs/api.html#require-requireactual-modulename

Context: Using latest TypeScript and React Native. All source and test files are written in TypeScript. Using a tsprocessor for Jest.

Printing out the module that I intend to test seems to indicate that it is mocked, even when I explicitly told it not to mock this module:

{ MyClass: 
   { [Function: MyClass]
     _isMockFunction: true,
     _getMockImplementation: 
      { [Function]
        _isMockFunction: true,
        _getMockImplementation: [Function],
        mock: [Object],
        mockClear: [Function],
        mockReturnValueOnce: [Function],
        mockReturnValue: [Function],
        mockImplementationOnce: [Function],
        mockImpl: [Function],
        mockImplementation: [Function],
        mockReturnThis: [Function] },
     mock: { calls: [], instances: [] },
     mockClear: [Function],
     mockReturnValueOnce: [Function],
     mockReturnValue: [Function],
     mockImplementationOnce: [Function],
     mockImpl: [Function],
     mockImplementation: [Function],
     mockReturnThis: [Function] } }

[vvo]

jest.unmock('../moduleName') should work as expected if the path to the module is the same as the import done in the code you are testing

[calclavia]

@vvo Here's a more specific example that did not work:

My test file (I'm trying to test TwitterProtocol module):

jest.unmock('../twitterProtocol')
import { TwitterProtocol } from '../twitterProtocol'

I believe the above code is correct?

[vvo]

I believe the above code is correct?

Yes this should work, can you create a simple repository test folder on github so we can investigate?

[cpojer]

Thanks for opening an issue. imports in TypeScript work similarly to ES2015 – they are hoisted above all other statements. When using babel-jest, we actually hoist unmock calls above imports. If you are using TypeScript, we don't have this custom transform available unfortunately.

Here are a few ways to work around this issue:

• Disable automocking completely ("automock": false) in the config.
• Instead of import, use require inside of your test files.
• Use babel-jest in your typescript preprocessor after processing your typescript code into JS. (basically: return babelJest.process(tsOutput, filename); ).
• Create a separate module that unmocks specific modules (not recommended).

Of course, the right way to fix this would be a plugin for typescript that hoists jest.unmock calls.

[calclavia]

@cpojer Would such a plugin for TypeScript be difficult to make? If it's not too difficult, I can give it a shot.

[cpojer]

I don't know, does TypeScript have a plugin system like babel does or is the compiler still completely closed?

[aaronabramov]

@cpojer would it make sense to run babel-preset-jest transformation on top of anything that is not babel-jest?
this would solve the coverage problem too

[aaronabramov]

so basically.. if you're using babel-jest you get babel-plugin-jest-hoist and babel-plugin-istanbul for free as a last step in your babel pipeline.
If you're using typescript/coffeescript/whatever, we'll jest run these two as a second transformation step. Performance would suck, but will solve a lot of issues

[cpojer]

It's definitely ok if we go down this route. I wouldn't mind for everything that doesn't use babel already.

At FB, we use our custom preprocessor and we need to make sure we don't double process there – what kind of escape-hatch can you think of for this use-case?

To summarize:

• babel-jest should do coverage instrumentation and hoist Jest calls.
• babel-jest will be used to transform coverage even when a different transformer is used.
• when not using babel-jest, but you are not using a custom preprocessor that uses babel, like at FB, don't use babel-jest at all.

[github-actions]

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