I've been reading through the Jasmine documentation and I've been struggling to understand what the Spies .and.stub method actually does. English is not my native language, so I don't even know what the word stub actually means, and there is no translation for it in my language.

In the documentation it says:

When a calling strategy is used for a spy, the original stubbing behavior can be returned at any time with and.stub.

describe(A spy, function() {  



var foo, bar = null;



  beforeEach(function() {

    foo = {

      setBar: function(value) {

        bar = value;

      }

    };



    spyOn(foo, 'setBar').and.callThrough();

  });



  it(can call through and then stub in the same spec, function() {

    foo.setBar(123);

    expect(bar).toEqual(123);



    foo.setBar.and.stub();

    bar = null;



    foo.setBar(123);

    expect(bar).toBe(null);

  });

});

What does and.stub actually do and how is it useful?