Testing jQuery.ajax with deferred method - .done() and .fail()

test_ajax_deferred.js

// Probably best to have this within setup
var ajaxStub = sinon.stub($, "ajax", function(event) {
  var result = $.Deferred();
  result.args = event;
  return result;
});

// Usage example
var call = theAjaxCallToTest()
// OR (if theAjaxCallToTest() doesn't return the actual ajax call)
theAjaxCallToTest();
var call = $.ajax.getCall(0).returnValue

// To get the arguments initially passed into ajax call
call.args;

// To return successful ajax call (having used .done() )
call.resolve({ data: "data to be returned after .done()" });

// To return failing ajax call (having used .fail() )
call.reject({ data: "data to be return after .fail()" });

@yairEO to restore the stub.