ES2016 Class, Sinon Stub Constructor

Question

I am trying to drown out a super call with Sinon and es2016, but I was not very lucky. Any ideas why this is not working?

Starting Node 6.2.2, this can be a problem when implementing classes / constructors.

.babelrc file:

{
  "presets": [
    "es2016"
  ],
  "plugins": [
    "transform-es2015-modules-commonjs",
    "transform-async-to-generator"
  ]
}

Test:

import sinon from 'sinon';

class Foo {
  constructor(message) {
    console.log(message)
  }
}

class Bar extends Foo {
  constructor() {
    super('test');
  }
}

describe('Example', () => {
  it('should stub super.constructor call', () => {
    sinon.stub(Foo.prototype, 'constructor');

    new Bar();

    sinon.assert.calledOnce(Foo.prototype.constructor);
  });
});

Result:

test
AssertError: expected constructor to be called once but was called 0 times
    at Object.fail (node_modules\sinon\lib\sinon\assert.js:110:29)
    at failAssertion (node_modules\sinon\lib\sinon\assert.js:69:24)
    at Object.assert.(anonymous function) [as calledOnce] (node_modules\sinon\lib\sinon\assert.js:94:21)
    at Context.it (/test/classtest.spec.js:21:18)

Note : this problem occurs only for designers. I can track methods inherited from the parent class without any problems.

Answer 1

You need spyinstead stub,

sinon.spy(Foo.prototype, 'constructor');

describe('Example', () => {
  it('should stub super.constructor call', () => {
    const costructorSpy = sinon.spy(Foo.prototype, 'constructor');
    new Bar();
    expect(costructorSpy.callCount).to.equal(1);
  });
});

***** Update ****** The above was not as expected, I added this path and now works.

 describe('Example', () => {
    it('should stub super.constructor call', () => {
      const FooStub = spy(() => sinon.createStubInstance(Foo));
      expect(FooStub).to.have.been.calledWithNew;
    });
 });

Answer 2

. , , :

class FakeSchema {
  constructor(newCar) {
    this.constructorCallTest();
    this.name = newCar.name;
  }

  constructorCallTest() {
    mochaloggger.log('constructor was called');
  }

}

// spy that tracks the contsructor call
var fakeSchemaConstrSpy = sinon.spy(FakeCarSchema.prototype,'constructorCallTest');

,

Answer 3

If you are in a browser environment, the following also works:

let constructorSpy = sinon.spy(window, 'ClassName');

For example, this will work with Jasmine.

Mocha instead runs in a Node environment, no window. The variable you are looking for isglobal