Add callsFake

[edeustace]

This adds callsFake function similar to the jasmine's callFake

The benefits of such a function is that you can add a mock function inline with the parameters of the function declared. I find this easier to read than callsArgWith as this requires you to think about the function you want to mock in a different way. I find it more natural and readable sometimes to drop in a replacement function.

example:

    var foo = {
       bar: function(a, b, c){
           // do stuff..
           return 'baz';
        },
        barWithCallback: function(a, callback){
          callback(null, 'ok');
        }
    }

    foo.bar = sinon.stub.create().callsFake(function(a, b, c){
      return 'baz';  
    });

    //more readable than callsArgWith(1, null, 'ok');?
    foo.barWithCallback = sinon.stub.create().callsFake(function(a, callback){
      callback(null, 'ok');
    });

[mantoni]

Can you explain what the difference is to these two use cases:

foo.barWithCallback = sinon.stub().yields(null, 'ok');

or

foo.barWithCallback = sinon.spy(function (a, callback) {
  callback(null, 'ok');
});

Thanks.

[edeustace]

Ah - my apologies - I didn't see the sinon.spy(function(){}) api when going through the docs.