Can I call the original method inside the supplied function to "andCallFake" of a Jasmine spy?

Question

I could save the original method in a variable in beforeEach, and then restore it in afterEach, but maybe I can use a spy which will be reset automatically between test suites.

spyOn(Ext, "create").andCallFake(function(className){
    if (className === 'Waf.view.Viewport')
        // call the original Ext.create method
});

Is this possible? I am using Jasmine 1.3

Answer 1

You can bind the original method into the fake:

var obj = {
  method: function(name) { return name + '!'; }
}

var methodFake = function(original, name) {
  return 'faked ' + original(name);
}.bind(obj, obj.method)
spyOn(obj, 'method').andCallFake(methodFake);

obj.method('hello') // outputs 'faked hello!'

For what it's worth, I don't think it's great practice to do this, but the need came up for me recently when I was testing some d3 code. Hope it helps.

Answer 2

This is a hack for Jasmine 2.3. Ideally the fake callback should have access to the reference of the original function to call as needed instead of dancing around like this.

Given that stubbing strategy can be modified on the fly in Jasmine 2.3, the following approach seems to work as well:

var createSpy = spyOn(Ext, "create");
createSpy.and.callFake(function(className){
    if (className === 'Waf.view.Viewport'){
        createSpy.and.callThrough();
        Ext.create(className);        
    }
});