How to unit test knockout.js subscribe functions with jasmine?

@kadin 

To unit test Knockout.js subscribe functions with Jasmine, you can follow the below steps:

1. Set up your test environment by including Jasmine and Knockout.js libraries in your test file.
2. In your test file, create a test suite using Jasmine's describe function.
3. Within the test suite, create a test case using Jasmine's it function.
4. Within the test case, create a mock object for the observable property that the subscribe function is attached to.
5. Set up the mocked observable property with a dummy value.
6. Create a spy using Jasmine's jasmine.createSpy function to monitor the subscribe function.
7. Call the subscribe function on the observable property with the spy as the argument.
8. Trigger the event that would normally trigger the subscribe function, like changing the value of the observable property.
9. Use Jasmine's expect function to create an assertion that checks if the spy was called with the expected arguments.
10. Run your tests using a test runner like Karma or Jasmine to verify that the subscribe function is working correctly.

Here is an example code snippet demonstrating how to unit test a subscribe function using Jasmine:

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describe('subscribe function test', function() {
  it('should call the subscribe function when the observable property changes', function() {
    var mockObservable = ko.observable(0);
    var spy = jasmine.createSpy('spy');

    mockObservable.subscribe(spy);

    // Change the value of the observable property
    mockObservable(1);

    expect(spy).toHaveBeenCalled();
    expect(spy).toHaveBeenCalledWith(1);
  });
});

By following these steps and guidelines, you can effectively unit test Knockout.js subscribe functions using Jasmine.