Watch and rerun Jest JS tests

The Jest documentation suggests using npm test to execute tests.

Is there a way of watching your source and tests to rerun Jest tests automatically when relevant files have been changed?

Thanks to Erin Stanfill for pointing out, Jest already has support for automatically re-running. The better configuration for package.json would be

{
  "scripts": {
    "test": "jest"
  }
}

To turn on the watch mode, just use

$ npm run test -- --watch

Or

$ yarn run test --watch

If you have npm test configured, you can just run npm test -- --watch.

Start you tests in watch mode.

jest --watch fileName.test.js

As per documentation

Run tests that match this spec name (match against the name in describe or test, basically).

jest -t name-of-spec
// or in watch mode
jest --watch -t="TestName"

1. install a couple of Grunt packages:

   npm install grunt-contrib-watch grunt-exec --save-dev
   

2. make a Gruntfile.js with the following:

   module.exports = function(grunt) {
   	grunt.initConfig({
   		exec: {
   			jest: 'node node_modules/jest-cli/bin/jest'
   		},
   		watch: {
   			files: ['**/*.js'],
   			tasks: ['exec:jest']
   		}
   	});
   	grunt.loadNpmTasks('grunt-contrib-watch');
   	grunt.loadNpmTasks('grunt-exec');
   }
   

3. then simply run:

   grunt watch
   

This example shows how to use gulp to run your Jest tests using jest-cli, as well as a tdd gulp task to watch files and rerun Jest tests when a file changes:

var gulp = require('gulp');
var jest = require('jest-cli');

var jestConfig = {
    rootDir: 'source'
};

gulp.task('test', function(done) {
    jest.runCLI({ config : jestConfig }, ".", function() {
        done();
    });
});

gulp.task('tdd', function(done) {
    gulp.watch([ jestConfig.rootDir + "/**/*.js" ], [ 'test' ]);
});

gulp.task('default', function() {
    // place code for your default task here
});

As a complement suggestion you can add "--watchAll" into your package.json file like this:

"scripts": {       
  "test": "jest --watchAll"
},

Each time you run npm test, the watch mode will be enable by default.

For more info npm CLI docs

If you want to run a single file in watch mode:

yarn run test --watch FileName.test.jsx

I personally use the npm package jest-watch-typeahead.

You need to do 3 steps:

1. Install npm packege:

> npm install --save-dev jest jest-watch-typeahead

2. Add to jest.config.js next code:

> module.exports = { > watchPlugins: [ > 'jest-watch-typeahead/filename', > 'jest-watch-typeahead/testname', > ], > };

3. Run Jest in watch mode

> yarn jest --watch