@libj/tbench

Overview

A "test bench" tools set for testing JavaScript / TypeScript code with comfort.
Based on sinon.js library.
All mocks are sinon stubs.

Features

• convenient API
• unit test itself

Mocks

ModuleMock

Mocks any JavaScript module.

API

function ModuleMock(
  module: string | Object,
  sinon: SinonSandbox = sinon.createSandbox(),
)

• module: npm module name or custom module
• sinon: custom instance of SinonSandbox

NPM module

import * as fs from 'fs'
import { ModuleMock } from '@libj/tbench'

const mock = ModuleMock('fs')
mock.existsSync.withArgs('/foo/bar.json').returns(true)

fs.existsSync('/foo/bar.json') // => true

Custom module

// myFoo.js
export const myFoo = () => 'foo'

// myBar.js
import { myFoo } from './myFoo.js'

export const myBar = () => myFoo()

// myBar.test.js
import { ModuleMock } from '@libj/tbench'
import * as MyFooModule from './myFoo.js'
import { myBar } from './myBar.js'

describe('myBar()', () => {
  it('calls myFoo()', () => {
    const mock = ModuleMock(MyFooModule).myFoo
    mock.returns('The Foooo')

    expect(myBar()).toBe('The Foooo')
  })
})

More examples

See in specs.

ClassMock

Mocks instances of classes.

API

function ClassMock(module: Object)
function ClassMock(module: Object, spec: Object)
function ClassMock(module: Object, spec: Object, sinon: SinonSandbox)
function ClassMock(module: Object, sinon: SinonSandbox)

• module: Custom module which holds class export
• spec: Specification object on how to mock the instance of class
• sinon: custom instance of SinonSandbox

Asserting constructor call

// MyFooClass.js
export class MyFooClass {}

// myBar.js
import { MyFooClass } from './MyFooClass'

export const myBar = arg => new MyFooClass(arg)

// myBar.test.js
import { ClassMock } from '@libj/tbench'
import * as MyFooClassModule from './MyFooClass'
import { myBar } from './myBar'

describe('myBar()', () => {
  it('constructs class with arg', () => {
    const mock = ClassMock(MyFooClassModule)
    mock.$constructor

    myBar('Foxy Lady')

    expect(mock.$constructor.calledOnce).toBeTruthy()
    expect(mock.$constructor.getCall(0).args).toEqual(['Foxy Lady'])
  })
})

(!) CAUTION: This will not differentiate if class has been called with or without new !

Mock class instance properties

// MyFooClass.js
export class MyFooClass {
  constructor() {
    this.foo = 'Initial Foo'
    this.bar = 'Initial Bar'
  }
}

// myBar.js
import { MyFooClass } from './MyFooClass'

export const myBar = () => new MyFooClass()

// myBar.test.js
import { ClassMock } from '@libj/tbench'
import * as MyFooClassModule from './MyFooClass'
import { myBar } from './myBar'

describe('myBar()', () => {
  it('proxies class instance properties', () => {
    const mock = ClassMock(MyFooClassModule, {
      foo: 'The Foo',
      bar: null,
    })
    mock.foo
    mock.bar.value('At the Bar')

    const res = myBar()

    expect(res.foo).toBe('The Foo')
    expect(res.bar).toBe('At the Bar')
  })
})

(i) Mind how mock values are initialized for foo and bar props
(i) Mock property has to be accessed even if initialized to trigger mocking
(i) It is always possible to overwrite initialized values at any time with any conditions (see sinon stubs)
(i) See respective specs for more examples

Mock class instance methods

// MyFooClass.js
export class MyFooClass {
  foo() {}
  bar() {}
}

// myBar.js
import { MyFooClass } from './MyFooClass'

export const myBar = () => new MyFooClass()

// myBar.test.js
import { ClassMock } from '@libj/tbench'
import * as MyFooClassModule from './MyFooClass'
import { myBar } from './myBar'

describe('myBar()', () => {
  it('proxies class instance methods', () => {
    const mock = ClassMock(MyFooClassModule, {
      'foo()': null,
      'bar()': 'The Bar from Method',
    })
    mock.foo.returns('And The Foo')
    mock.bar

    const o = myBar()

    expect(o.foo()).toBe('And The Foo')
    expect(o.bar()).toBe('The Bar from Method')
  })
})

(i) Method mocks are denoted using parenthesis
(i) Mind how mock values are initialized for foo() and bar() methods
(i) It is always possible to overwrite initialized values at any time with any constraints
(i) See respective specs for more examples

Restoring single mock only

// test.js
import { ClassMock } from '@libj/tbench'

describe('FooTest', () => {
  let mock

  beforeEach(() => {
    mock = ClassMock(FooClassModule)
  })

  afterEach(() => {
    mock.$restore()
  })
});

(i) Applies to both ModuleMock / ClassMock

Restoring all mocks at once

This can be controlled via custom sinon instance

// test.js
import * as sinonLib from 'sinon'
import { ModuleMock, ClassMock } from '@libj/tbench'

describe('FooTest', () => {
  let sinon, moduleMock, classMock

  beforeEach(() => {
    sinon = sinonLib.createSandbox()
    moduleMock = ModuleMock('fs', sinon)
    classMock = ClassMock(FooClassModule, sinon)
  })

  afterEach(() => {
    sinon.restore()
  })
});

Using in pure NodeJS code

In order for mocks to be working in raw nodejs code imports should be done using module as whole.

// foo.js
const foo = () => {}

module.exports = { foo }

// bar.js
const FooModule = require('./foo.js')

const bar = () => FooModule.foo()

module.exports = { bar }

(i) Notice how import is done in bar.js
(i) This is applied to both ModuleMock and ClassMock