sinon.assert.calledWith methods fails because fake is not a spy

[kvernon]

We understand you have a problem and are in a hurry, but please provide us with some info to make it much more likely for your issue to be understood, worked on and resolved quickly.

• Sinon version : 2.3.5
• Environment : mocha / mac / nodejs
• Example URL :
• Other libraries you are using:

What did you expect to happen?
I expected the test to process the stub... Your documentation states it does:
http://sinonjs.org/releases/v2.3.5/assertions/

Sinon.JS ships with a set of assertions that mirror most behavior verification methods and properties on spies and stubs. The advantage of using the assertions is that failed expectations on stubs and spies can be expressed directly as assertion failures with detailed and helpful error messages.

The assertions can be used with either spies or stubs.

What actually happens
expected [AssertError: fake is not a spy] to equal null

How to reproduce

Describe with code how to reproduce the faulty behaviour,
or link to code on JSBin or similar

describe('example test', () => {
  it('should evaluate sinon.assert.calledWith', () => {
    const stub = sinon.stub();
    const call1 = stub.onCall(0).resolves(true).stub;

    const itemToEval = (option) => {
      return stub(option);
    };

    return itemToEval(1).then(data => {
      expect(data).to.equal(true); //passes
      sinon.assert.calledWith(call1, 1); //fake is not a spy
    });

  });
});

Really long code sample or stacktrace

If you need to provide a dump of a stack trace or
other lengthy material, such as 80 lines of example code,
please stuff it in a `<details>` tag such as this
to make the issue more readable. Thanks.

See this for an example

[fatso83]

You are using the .stub property. That is an internal detail of Sinon. The stub we talk about is the one returned from the stub() method - or any of the chained calls. This runs fine:

var expect = require('chai').expect;
var sinon =require('sinon');
describe('example test', () => {
  it('should evaluate sinon.assert.calledWith', () => {
    const stub = sinon.stub();
    const call1 = stub.onCall(0).resolves(true) // don't use `.stub`;

    const itemToEval = (option) => {
      return stub(option);
    };

    return itemToEval(1).then(data => {
      expect(data).to.equal(true); //passes
      sinon.assert.calledWith(call1, 1); // passes
      sinon.assert.calledWith(stub, 1); // passes
    });

  });
});