Medium - Dynamically matching files in Jest - using environment variable

.env

JEST_FILES_PATTERN="spec"
// or JEST_FILES_PATTERN="test"
// or JEST_FILES_PATTERN="spec|test"

jest.config.js

require('dotenv').config()
module.exports = {
  roots: [
    '<rootDir>/dist/',
  ],
  testEnvironment: 'node',
  transform: {
    '^.+\\.(ts|tsx)$': 'ts-jest',
  },
  testMatch: [`**/?(*.)+(${process.env.JEST_FILES_PATTERN}).js`]
}

package.json

{
  ...
  "scripts": {
    ...
    "build": "rm -rf dist && tsc",
    "pretest": "yarn build",
    "test": "yarn jest --passWithNoTests"
  }
}