Watch and rerun Jest JS tests - npm

Question

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?

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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"

Answer 5

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
});

Answer 6

install a couple of Grunt packages:
npm install grunt-contrib-watch grunt-exec --save-dev
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');
}
then simply run:
grunt watch

Answer 7

If you want to run a single file in watch mode:
yarn run test --watch FileName.test.jsx

Answer 8

I personally use the npm package jest-watch-typeahead.
You need to do 3 steps:
Install npm packege:
npm install --save-dev jest jest-watch-typeahead
Add to jest.config.js next code:
module.exports = {
watchPlugins: [
'jest-watch-typeahead/filename',
'jest-watch-typeahead/testname',
],
};
Run Jest in watch mode
yarn jest --watch