What sets apart .andReturn(...) from .respondWith(...) when running AJAX call tests in JavaScript using Jasmine?

Question

What sets apart .andReturn(...) from .respondWith(...) when running AJAX call tests in JavaScript using Jasmine?

While utilizing the jasmine-ajax library for testing JavaScript code, I have discovered a way to mock ajax responses. There are essentially two methods to achieve this:

Method #1:

jasmine.Ajax.requests.mostRecent().respondWith({
  status: 200,
  contentType: 'text/plain',
  responseText: 'my response'
});

Method #2:

jasmine.Ajax.stubRequest('my/url').andReturn({
  'responseText': 'my response'
});

If my mostRecent request corresponds to the url my/url, what sets these two approaches apart?

I first came across these techniques in M.E. Trostler's "JavaScript Unit Testing" video series, however, I am unable to find a definitive answer to my query in those videos, StackOverflow, or even in the Jasmine online documentation for its ajax.js plugin.

javascript ajax unit-testing jasmine

Answer 1

Answer №1

Upon conducting further research independently, I have come to the conclusion that the disparity between these two commands is largely related to the timing of the response from the mocked ajax call. In essence:

respondWith issues a response to a previous unanswered ajax call immediately,
andReturn sets up a response to be sent as soon as a future ajax call is made.

In the subsequent 2 examples, it is evident that verifying the callback within the onreadystatechange handler determines whether a response to an ajax call has been received, as this would trigger the callback. In method #1, the ajax call is made but remains unanswered until respondWith is invoked. In contrast, in approach #2, the response is pre-configured so that when the ajax call is initiated, a response is returned promptly.

Method #1:

setUpAndSendAjaxCall1();
expect(onreadystatechangeCallback1).not.toHaveBeenCalled();
jasmine.Ajax.requests.mostRecent().respondWith({
  ...
  "responseText": "response #1"
});
expect(onreadystatechangeCallback1).toHaveBeenCalledWith("response #1");

Method #2:

jasmine.Ajax.stubRequest(myUrl).andReturn({
  ...
  "responseTest": "response #2"
});
setUpAndSendAjaxCall2();
expect(onreadystatechangeCallback2).toHaveBeenCalledWith("response #2");

Answer 2

Upon conducting further research independently, I have come to the conclusion that the disparity between these two commands is largely related to the timing of the response from the mocked ajax call. In essence:

respondWith issues a response to a previous unanswered ajax call immediately,
andReturn sets up a response to be sent as soon as a future ajax call is made.

In the subsequent 2 examples, it is evident that verifying the callback within the onreadystatechange handler determines whether a response to an ajax call has been received, as this would trigger the callback. In method #1, the ajax call is made but remains unanswered until respondWith is invoked. In contrast, in approach #2, the response is pre-configured so that when the ajax call is initiated, a response is returned promptly.

Method #1:

setUpAndSendAjaxCall1();
expect(onreadystatechangeCallback1).not.toHaveBeenCalled();
jasmine.Ajax.requests.mostRecent().respondWith({
  ...
  "responseText": "response #1"
});
expect(onreadystatechangeCallback1).toHaveBeenCalledWith("response #1");

Method #2:

jasmine.Ajax.stubRequest(myUrl).andReturn({
  ...
  "responseTest": "response #2"
});
setUpAndSendAjaxCall2();
expect(onreadystatechangeCallback2).toHaveBeenCalledWith("response #2");

What sets apart .andReturn(...) from .respondWith(...) when running AJAX call tests in JavaScript using Jasmine?

Answer №1

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