Jest coverage shows grey 0% for files exporting plain objects.

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

What is the current behavior? Before running an app, I generate some files that export plain objects (e.g. environment variables).

Here’s one such example.

export default {
  someKey: "someValue"
}

These are tested with Jest snapshots to check they haven’t changed against expectations. In the past, such files would be included in tests and reported as green after running a simple snapshot test.

Now, Jest appears to show 0% for all columns in these files, but the row is not red, but rather grey. I wonder if this is a new behaviour? The tests still run and snapshots get generated.

What is the expected behavior? Row should be green with 100% coverage.

Please provide your exact Jest configuration

"jest": {
    "collectCoverageFrom": [
      "src/**/*.{js,jsx}"
    ],
    "coveragePathIgnorePatterns": [
      "storybook.(js|jsx)"
    ],
    "setupFiles": [
      "<rootDir>/config/polyfills.js",
      "<rootDir>/config/jest/setup.js"
    ],
    "testMatch": [
      "<rootDir>/**/__tests__/**/*.js?(x)",
      "<rootDir>/src/**/?(*.)(spec|test).js?(x)"
    ],
    "testEnvironment": "node",
    "testURL": "https://localhost",
    "transform": {
      "^.+\\.(js|jsx)$": "<rootDir>/node_modules/babel-jest",
      "^.+\\.css$": "<rootDir>/config/jest/cssTransform.js",
      "^(?!.*\\.(js|jsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
    },
    "transformIgnorePatterns": [
      "[/\\\\]node_modules[/\\\\].+\\.(js|jsx)$"
    ],
    "moduleNameMapper": {
      "^react-native$": "react-native-web",
      "^.+\\.css$": "identity-obj-proxy"
    },
    "moduleFileExtensions": [
      "web.js",
      "js",
      "json",
      "web.jsx",
      "jsx"
    ]
  },

Run npx envinfo --preset jest in your project directory and paste the results here

  System:
    OS: macOS High Sierra 10.13.4
    CPU: x64 Intel(R) Core(TM) i7-2720QM CPU @ 2.20GHz
  Binaries:
    Node: 9.8.0
    Yarn: 1.5.1
    npm: 5.6.0
  npmPackages:
    jest:
      wanted: 22.4.3
      installed: 22.4.3

[SimenB]

I don’t think this is something Jest has changed, this should be reported to Istanbul.

I think it says 0% since there is no executable code there.

Mind opening up an issue with istanbul and linking back here? Happy to reopen if the issue is in Jest

[ashleymoogle]

Hello! I know this issue is kinda old but I had the same issue and fixed it like so: old env.js:

export default {
 value: true
}

old test:

import env from './env'
it('should have a value', () => {
    expect(env.value).toBeTruthy()
})

NEW AND WORKING: env.js:

const env = () => {
 return {
  value: true
 }
}
export default env

new test with coverage working:

import env from './env'
it('should have a value', () => {
    expect(env().value).toBeTruthy()
})

Tl;dr SimenB was right, its because the code was not executed. Funny enough that lack of coverage started appearing after I updated jest to the latest version. Cheers.