Memory leak reported by detectLeaks for minimal coverage example

[rickhanlonii]

Do you want to request a feature or report a bug?

Bug

What is the current behavior?

Current behavior is for --detectLeaks to report a leak for any --coverage enabled test (which has at least one import)

Reproduction Steps

Steps to repo:

• Clone https://github.com/rickhanlonii/jest-coverage-leak
• yarn
• yarn test:pass (this is jest --detectLeaks module.spec.js)
• yarn test:fail (this is jest --detectLeaks module.spec.js --coverage)

What is the expected behavior?

Expect that --detectLeaks does not fail for minimal --coverage test

Versions

• jest@22.0.6
• yarn@1.3.2
• node@8.9.4
• npm@5.6.0
• macOS@10.13.1

More information

Using the new detectLeaks feature I was able to create a minimal expample repo of a leak when ever coverage is enabled:

// module.js
const noOp = () => {};
module.exports = noOp;

// module.spec.js
const _ = require('./module.js');

test('empty test', () => {
  expect(true).toBeTruthy();
});

Screens

Pass:

Fail:

A few notes:

• The module is not used in the test, only imported
• Commenting out the import will pass with coverage
• Moving the module function into the test file will pass
• This is only Jest (i.e. no babel-jest or React)

[rickhanlonii]

I think the next step is probably to figure out if this is an error with the detectLeaks reporting or if it's a legit leak

[github-actions]

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