Why do I have to call spyOn in a beforeEach()?

问题

I have a simple test suite that has one it function inside of it. I want to see if a certain function is called within the function I'm calling, so I have something like this:

describe("doStuff", function () {
    var foo = new Foo();
    spyOn(foo, "doOtherStuff");
    foo.doStuff(true);
    it("should do stuff and other stuff", function() {
        expect(foo.stuffDone).toBe(true);
        expect(foo.doOtherStuff).toHaveBeenCalled();
    });
});

However, this gives me the error: Expected a spy, but got Function.

After looking around some, I saw all examples had the spyOn in a beforeEach. So, I changed my test to:

describe("doStuff", function () {
    var foo = new Foo();
    beforeEach(function() {
        spyOn(foo, "doOtherStuff");
        foo.doStuff(true);
    });
    it("should do stuff and other stuff", function() {
        expect(foo.stuffDone).toBe(true);
        expect(foo.doOtherStuff).toHaveBeenCalled();
    });
});

And this works. I'm pretty new to jasmine, so I may just be missing something obvious, but I just want to know why it has to be in a beforeEach for the spyOn to work. It's easy enough to just use the beforeEach, but I want to understand better what is going on. Thanks.

回答1:

That is simply because Jasmine runs the Specs in a different closure. The describe and it calls only register callbacks that are added to a queue and then executed by Jasmine later. And Jasmine always cleans up the spies ...

But you can also add the spyOn to the it callback.

来源：https://stackoverflow.com/questions/13480214/why-do-i-have-to-call-spyon-in-a-beforeeach

标签

javascript

unit-testing

jasmine