Improving the Jest tests performance in CI environments when using Typescript - Medium Story

Jenkinsfile

pipeline {
    agent { docker { image 'node:18.7-alpine' } }
    stages {
        stage('test') {
            steps {
                sh 'npm run test:ci'
            }
        }
    }
}

jest.config.js

const isolatedModules = process.env.ISOLATED_MODULES === 'true';
module.exports = {
  // [...]
  globals: {
    'ts-jest': {
      isolatedModules
    }
  }
};

package.json

{
  "scripts": {
    "test": "jest",
    "test:ci": "ISOLATED_MODULES=true node --expose-gc ./node_modules/.bin/jest --runInBand"
  }
}