jest: jest --watch fails to determine files to run tests against if there are changes since last commit

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

Bug

What is the current behavior?

We have an angular project using jest. Jest uses git to determine file changes and run tests against these files.

Clean project

If the project is “clean” with no change since last commit, then running jest --watch starts properly. Then we can use it normally, it detects changes properly and run expected tests suits.

Dirty project

if the projects has changes on certain files since last commit and we try to run jest --watch then Jest struggles to start and stay forever on the Determining test suites to run... state. Any change after that doesn’t change the stuck jest state.

If we revert our changes (nothing to be commited) then retry to launch jest --watch works. So it seems it’s a real problem with git changes detection by Jest.

Environment

This behavior is always encountered on windows. And sometimes on mac OS.

What is the expected behavior?

Being able to run jest --watch even if there are modified files since last commit. If the changes files are not detected properly we expect to be able to even load jest and being able to pattern filter on the files we want.

Please provide your exact Jest configuration

module.exports = {
  setupTestFrameworkScriptFile: "<rootDir>/src/setupJest.ts",
  globals: {
    'ts-jest': {
      'tsConfigFile': 'src/tsconfig.spec.json'
    },
    '__TRANSFORM_HTML__': true
  },
  transform: {
    '^.+\\.(ts|js|html)$': '<rootDir>/node_modules/jest-preset-angular/preprocessor.js',
  },
  testMatch: [
    "**/__tests__/**/*.+(ts|js)?(x)",
    "**/+(*.)+(spec).+(ts|js)?(x)"
  ],
  moduleFileExtensions: [
    'ts',
    'js',
    'html'
  ],
  moduleNameMapper: {
    "assets/(.*)": "<rootDir>/src/assets/$1"
  },
  transformIgnorePatterns: [
    'node_modules/(?!@ngrx)'
  ],
  coverageReporters: ['html', 'text-summary', 'text']
};

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

System:
    OS: Windows 10
    CPU: x64 Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
  Binaries:
    Yarn: 1.6.0 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 5.8.0 - C:\Program Files\nodejs\npm.CM

  System:
    OS: macOS High Sierra 10.13.4
    CPU: x64 Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
  Binaries:
    Node: 8.11.1 - /usr/local/bin/node
    Yarn: 1.6.0 - /usr/local/bin/yarn
    npm: 5.6.0 - /usr/local/bin/npm
  npmPackages:
    @types/jest: 22.2.3 => 22.2.3
    jest: 22.4.3 => 22.4.3