mockalicious

Keep on mocking in the free world

Module mocking for both native ESM and CJS environments

Install

npm i mockalicious

API

mockalicious(fileUrlOrPath) => loader

Initialize a module loader that can load a module with defined mocks.

ESM:

const load = mockalicious(import.meta.url)

CJS:

const load = mockalicious(__filename)

Always initialize before any tests

loader(entry, mocks) => Promise => entry module

Pass the loader an entry point to load and supply mocks for any modules in its dependency tree.

Example:

await loader('path/to/file/being/tested.js', {
  fs: {
    ...(await import('fs')), // copy original fs
    readFile() {
      // mock readFile function
    }
  },
  open () {
    // mock default exported function of ecosystem module `open`
  },
  './path/to/file.js'() {
    default () {
      // mock default exported function of local module  
    },
    bar: 1 // mock other exports
  }
})

Modes

Mocking native ESM modules demands the use of a loader, currently via Node's --experimental-loader flag. However in order to support running node directly without fiddling with flags, if the loader is not set mockalicious will use a worker thread to reload a test file with the loader. This comes with some trade offs.

Autoload Mode

Not setting the --experimental-loader flag will cause mockalicious to pause the main thread, run the tests in a worker with the --experimental-loader flag set and then exit the process.

This will work in most cases, based on what worker threads support. The following functionality in tests or tested code will fail in autoload mode:

• process.chdir
• any process methods for setting groups or ids
• capturing signals
• input from STDIN

Loader Mode

To use mockalicious in loader mode, set the --experimental-loader flag like so:

node --experimental-loader=mockalicious/loader.mjs my-test.js

Support

• Node 12.4/14+

License

ISC