es6 collaborator的模拟构造

Question

我有一个利用helper类的类，我想验证它是否正确地构造了这些对象。所以，我试图在我的类中存根“构造函数”方法，但我显然做得不对：

"use strict";

class Collaborator {
  constructor(settings) {
    console.log("Don't want this to be called!")
    this.settings = settings;
  }
}

class ThingToTest {
  constructor(settings) {
    this.helper = new Collaborator(settings);
  }
}

const assert = require("assert");
const sinon = require("sinon");

describe("ThingToTest", () => {
  let settings = "all the things"

  context("spying on constructor", () => {
    let spy = sinon.spy(Collaborator, "constructor")
    after(() => spy.restore()) 
    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        new ThingToTest(settings);
        sinon.assert.calledWith(spy, settings)
      })
    })
  })

  context("spying on prototype constructor", () => {
    let spy = sinon.spy(Collaborator.prototype, "constructor")
    after(() => spy.restore()) 
    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        new ThingToTest(settings);
        sinon.assert.calledWith(spy, settings)
      })
    })
  })

  context("stub constructor", () => {
    before(() => {
      sinon.stub(Collaborator, "constructor", (settings) => {
        console.log("This should be called so we can inspect", settings);
      })
    })
    after(() => { Collaborator.constructor.restore() }) 
    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        new ThingToTest(settings);
      })
    })
  })

  context("stub prototype constructor", () => {
    before(() => {
      sinon.stub(Collaborator.prototype, "constructor", (settings) => {
        console.log("This should be called so we can inspect", settings);
      })
    })
    after(() => { Collaborator.prototype.constructor.restore() }) 
    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        new ThingToTest(settings);
      })
    })
  })

})

运行此命令会产生以下(不需要的)结果：

ThingToTest
    spying on constructor
      constructor
Don't want this to be called!
        1) creates a Collaborator with provided settings
    spying on prototype constructor
      constructor
Don't want this to be called!
        2) creates a Collaborator with provided settings
    stub constructor
      constructor
Don't want this to be called!
        ✓ creates a Collaborator with provided settings
    stub prototype constructor
      constructor
Don't want this to be called!
        ✓ creates a Collaborator with provided settings

看起来存根在某种程度上是有效的，因为把存根测试放在间谍用可怕的"TypeError:尝试包装已经包装的构造函数“测试错误之前。因此，清楚地弄清楚如何模拟Collaborators构造函数只是我所做错误的一半。。。我也没有正确地恢复构造函数。有什么建议吗？

Answer 1

这不是我想要的解决方案，但是暂时我可能会使用这个(但是，如果你有什么建议，请把我从我自己身上拯救出来)：

context("checking Collaborator in a more integration style test", () => {
    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        let thing = new ThingToTest(settings);
        assert.equal(thing.helper.settings, settings)
      })
    })
  })

这将传递并验证协作者是否设置了正确的设置。但是现在，如果我想重构Collaborator构造函数，我将破坏ThingToTest。同样，我仍然希望有人能提出一种方法来对这个类进行实际的单元测试！

Answer 2

我不确定这是不是我的最终答案，但我最终还是使用了proxyquire，因为这是迄今为止我找到的最好的解决方案。为了展示它是如何工作的，我将测试中的类分离到它们自己的目录中，并将测试文件放在一个子" test“目录中。这说明了proxyquire中的路径是如何工作的(我花了一些时间才弄清楚)。所以，这就是我的结论：

/Collaborator.js

"use strict"

class Collaborator {
  constructor(settings) {
    console.log("Don't want this to be called!")
    this.settings = settings;
  }
}

module.exports = Collaborator

/ThingToTest.js

"use strict"

const Collaborator = require("./Collaborator")

class ThingToTest {
  constructor(settings) {
    this.helper = new Collaborator(settings)
  }
}

module.exports = ThingToTest

/test/ExampleTest.js

"use strict";

const proxyquire = require('proxyquire')
const mockCollaborator = sinon.stub();
const ThingToTest = proxyquire("../ThingToTest", { "./Collaborator" : mockCollaborator })

const assert = require("assert");
const sinon = require("sinon");

describe("ThingToTest", () => {
  let settings = "all the things"

  context("checking Collaborator in a more integration style test", () => {

    describe("constructor", () => {
      it("creates a Collaborator with provided settings", () => {
        let thing = new ThingToTest(settings);
        assert.equal(mockCollab.firstCall.calledWith(settings))
      })
    })
  })
})

注意proxyquire("../ThingToTest", { "./Collaborator" : mockCollaborator })中的路径如何匹配"ThingToTest“使用的内容，而不是来自测试类的路径。我希望这对其他人有所帮助，但我仍然对其他想法和建议持开放态度！