`jest --init` to set up package.json with default values

🚀 Feature Proposal

Much like other tools (tsc, tslint, etc), it would be very useful if there were an --init option for jest cli to supplement the existing package.json with all possible settings for jest, with their default values.

Motivation

This would make custom configuration easier: instead of having to refer to documentation every time, one could simply jest --init and look for the setting which describes what it does to edit that.

Example

# jest --init

Pitch

Because jest is the master of the configuration which is available – it makes sense that jest should be able to populate these settings. Ideally, this --init would also guide the user through some more common options, such as:

1. “Is this a TypeScript project?” (positive answer enables the ts-jest transform, alters “testMatch” to “**/.spec.ts", adds “ts” to “moduleFileExtensions”, adds "/.\.d\.td/” to “watchIgnorePatterns”, etc
2. “Do you want coverage reports?” (positive answer sets “coverageDirectory” to “coverage” (ignored by default with github .gitignore for node projects)
3. “Would you like Jest to use Jest for ‘npm test’?” (positive answer sets “test” npm script to “jest”)

Jest already provides probably the best test running framework I’ve used (between jasmine, mocha and jest), with so many things already baked in (coverage! What a win!) – it just seems like one of the aims of the project is to be as polished as possible. A guided --init would, imo, help a lot.

[SimenB]

This is done #6442

[ranyitz]

Typescript detection added:

I’ve added a short explanation for each option and changed the looks of the generated file:

// For a detailed explanation regarding each configuration property, visit:
// https://facebook.github.io/jest/docs/en/configuration.html

module.exports = {
  // All imported modules in your tests should be mocked automatically
  // automock: false,

  // Stop running tests after the first failure
  // bail: false,

  // Respect "browser" field in package.json when resolving modules
  // browser: false,

  // The directory where Jest should store its cached dependency information
  // cacheDirectory: "/var/folders/tz/39sb86z96tj_2cqqkm1kfkh9bwd75d/T/jest_ocrnot",

  // Automatically clear mock calls and instances between every test
  clearMocks: true,

  // Indicates whether the coverage information should be collected while executing the test
  // collectCoverage: undefined,

  // An array of glob patterns indicating a set of files for which coverage information should be collected
  // collectCoverageFrom: undefined,

  // The directory where Jest should output its coverage files
  coverageDirectory: "coverage",

  // An array of regexp pattern strings used to skip coverage collection
  // coveragePathIgnorePatterns: [
  //   "/node_modules/"
  // ],

  // A list of reporter names that Jest uses when writing coverage reports
  // coverageReporters: [
  //   "json",
  //   "text",
  //   "lcov",
  //   "clover"
  // ],

  // An object that configures minimum threshold enforcement for coverage results
  // coverageThreshold: undefined,

  // Make calling deprecated APIs throw helpful error messages
  // errorOnDeprecated: false,

  // Force coverage collection from ignored files usin a array of glob patterns
  // forceCoverageMatch: [],

  // A path to a module which exports an async function that is triggered once before all test suites
  // globalSetup: null,

  // A path to a module which exports an async function that is triggered once after all test suites
  // globalTeardown: null,

  // A set of global variables that need to be available in all test environments
  globals: {
    "ts-jest": {
      "tsConfigFile": "tsconfig.json"
    }
  },

  // An array of directory names to be searched recursively up from the requiring module's location
  // moduleDirectories: [
  //   "node_modules"
  // ],

  // An array of file extensions your modules use
  moduleFileExtensions: [
    "ts",
    "tsx",
    "js"
  ],

  // A map from regular expressions to module names that allow to stub out resources with a single module
  // moduleNameMapper: {},

  // An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
  // modulePathIgnorePatterns: [],

  // Activates notifications for test results
  // notify: false,

  // An enum that specifies notification mode. Requires { notify: true }
  // notifyMode: "always",

  // A preset that is used as a base for Jest's configuration
  // preset: null,

  // Run tests from one or more projects
  // projects: undefined,

  // Use this configuration option to add custom reporters to Jest
  // reporters: undefined,

  // Automatically reset mock state between every test
  // resetMocks: false,

  // Reset the module registry before running each individual test
  // resetModules: false,

  // A path to a custom resolver
  // resolver: undefined,

  // Automatically restore mock state between every test
  // restoreMocks: false,

  // The root directory that Jest should scan for tests and modules within
  // rootDir: undefined,

  // A list of paths to directories that Jest should use to search for files in
  // roots: undefined,

  // Allows you to use a custom runner instead of Jest's default test runner
  // runner: "jest-runner",

  // The paths to modules that run some code to configure or set up the testing environment before each test
  // setupFiles: undefined,

  // The path to a module that runs some code to configure or set up the testing framework before each test
  // setupTestFrameworkScriptFile: undefined,

  // A list of paths to snapshot serializer modules Jest should use for snapshot testing
  // snapshotSerializers: [],

  // The test environment that will be used for testing
  testEnvironment: "node",

  // Options that will be passed to the testEnvironment
  // testEnvironmentOptions: {},

  // Adds a location field to test results
  // testLocationInResults: false,

  // The glob patterns Jest uses to detect test files
  testMatch: [
    "**/__tests__/*.+(ts|tsx|js)"
  ],

  // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
  // testPathIgnorePatterns: [
  //   "/node_modules/"
  // ],

  // The regexp pattern Jest uses to detect test files
  // testRegex: "",

  // This option allows the use of a custom results processor
  // testResultsProcessor: null,

  // This option allows use of a custom test runner
  // testRunner: undefined,

  // This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
  // testURL: "about:blank",

  // Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
  // timers: "real",

  // A map from regular expressions to paths to transformers
  transform: {
    "^.+\\.(ts|tsx)$": "ts-jest"
  },

  // An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
  // transformIgnorePatterns: [
  //   "/node_modules/"
  // ],

  // An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
  // unmockedModulePathPatterns: undefined,

  // Indicates whether each individual test should be reported during the run
  // verbose: null,

  // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
  // watchPathIgnorePatterns: [],

  // Whether to use watchman for file crawling
  // watchman: true,
};

All undefined values should be corrected after #6428 will be merged.

@rickhanlonii Is that something we can start with?