Better tests, proxyquire vs injection vs mockless

injection-spec.js

var assert = require('assert')
var sinon = require('sinon')
var dependency = require('dependency')
var sut = require('./injection-sut')

describe('sut', function () {
  var methodStub

  beforeEach(function () {
    methodStub = sinon.stub(dependency, 'method')
  })

  afterEach(function () {
    dependency.method.restore()
  })

  it('should return value from call to dependency.method', function () {
    methodStub.returns('dependency.method.response')

    assert.equal(sut(dependency), 'dependency.method.response')

    assert(methodStub.calledOnce)
    assert.equal(methodStub.args[0][0], 'bagel')
  })
})

injection-sut.js

module.exports = function sut (dependency) {
  return dependency.method('bagel')
}

mockless-spec.js

var assert = require('assert')
var sut = require('sut')

describe('sut', function () {
  var dependency = {}

  it('should return value from call to dependency.method', function () {
    dependency.method = function (arg) {
      assert.equal(arg, 'bagel')
      return 'dependency.method.response'
    }

    assert.equal(sut(dependency), 'dependency.method.response')
  })
})

// Pros:
// * less setup/teardown code
// * straight forward asserts
// * vanilla (no devDependency modules)

// Cons:
// * It's possible to get false negatives. If dependency removes ".method",
     the test will still pass even though code doesn't work. (this is a big con)
// * Gets repetitive writing the method in every test.

require-spec.js

var proxyquire = require('proxyquire')
var assert = require('assert')
var sinon = require('sinon')
var dependency = require('dependency')

describe('sut', function () {
  var methodStub
  var sut

  beforeEach(function () {
    methodStub = sinon.stub(dependency, 'method')
    sut = proxyquire('./require-sut', {
      dependency: dependency
    })
  })

  afterEach(function () {
    dependency.method.restore()
  })

  it('should return value from call to dependency.method', function () {
    methodStub.returns('dependency.method.response')

    assert.equal(sut(), 'dependency.method.response')

    assert(methodStub.calledOnce)
    assert.equal(methodStub.args[0][0], 'bagel')
  })
})

// Pros:
// * Can't get a false negative

// Cons:
// * A lot of setup/teardown

require-sut.js

var dependency = require('dependency')

module.exports = function sut () {
  return dependency.method('bagel')
}