Stryker

Professor X: For someone who hates mutants... you certainly keep some strange company.
William Stryker: Oh, they serve their purpose... as long as they can be controlled.

Introduction

For an introduction to mutation testing and Stryker's features, see stryker-mutator.github.io.

Getting started

Stryker is a mutation testing framework for JavaScript. It allows you to test your tests by temporarily inserting bugs.

To install Stryker, execute the command:

$ npm install stryker stryker-api --save-dev

To test if Stryker is installed correctly, execute the command:

$ node_modules/.bin/stryker --version

This should print the latest version of Stryker.

Usage

$ node_modules/.bin/stryker <command> [options] [stryker.conf.js]

The main command for Stryker is run, which kicks off mutation testing.

By default, we expect a stryker.conf.js file in the current working directory. This can be overridden by specifying a different file as the last parameter.

Before your first run, we recommend you try the init command, which helps you to set up this stryker.conf.js file and install any missing packages needed for your specific configuration. We recommend you verify the contents of the configuration file after this initialization, to make sure everything is setup correctly. Of course, you can still make changes to it, before you run Stryker for the first time.

The following is an example stryker.conf.js file:

module.exports = function(config){
  config.set({
    files: ['test/helpers/**/*.js', 
            'test/unit/**/*.js', 
            { pattern: 'src/**/*.js', included: false, mutated: true },
            { pattern: 'src/templates/*.html', included: false, mutated: false },
            '!src/fileToIgnore.js'],
    testFramework: 'mocha',
    testRunner: 'mocha',
    mutator: 'es5',
    reporter: ['progress', 'clear-text', 'dots', 'html', 'event-recorder'],
    coverageAnalysis: 'perTest',
    plugins: ['stryker-mocha-runner', 'stryker-html-reporter']
  });
}

As you can see, the config file is not a simple JSON file. It should be a common js (a.k.a. node) module. You might recognize this way of working from the karma test runner.

Make sure you at least specify the files and the testRunner options when mixing the config file and/or command line options.

Command-line interface

Stryker can also be installed, configured and run using the Stryker-CLI. If you plan on using Stryker in more projects, the Stryker-CLI is the easiest way to install, configure and run Stryker for your project.

You can install the Stryker-CLI using:

$ npm install -g stryker-cli

The Stryker-CLI works by passing received commands to your local Stryker installation. If you don't have Stryker installed yet, the Stryker-CLI will help you with your Stryker installation. This method allows us to provide additional commands with updates of Stryker itself.

Supported mutators

See our website for the list of currently supported mutators.

Configuration

See the stryker's package readme for all config options.