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a lightweight javascript stubbing framework

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jstub

jstub is a lightweight javascript stubbing framework. jstub has no dependencies, although it will leverage
qunit if available. The jstub_tests.html file, which uses jquery and qunit to run, is the best place to look for real world usage example.

usage

You stub a method call via the $.stub function. In its simplest form, $.stub is called with 4 parameters.
The first is the object in which the function is define (global function live in @code@window@code@), the string name of the method, an array of expected parameters, and a return value. For example, say we wanted to test the following function:

//the internal implementation doesn't matter since we are mocking the getNewNotifications method
function getNewNotifications(level)
{
  var count = TODO;//hit the server and return the number of new notifications
  return count;
}

We would call:

$.stub(window, 'getNewNotifications', [1], 10);

Any subsequent calls to getNewNotifications(1); would return 10.

non ‘window’ methods

Stubbing a method that does not exist globally is equally as easy. Given:

$.blockUI =
{
  show: function(text)
  {
    //todo block the UI
    return $blockElement;
  }
}

We would call:

$.stub($.blockUI, 'show', ['Processing, Please Wait'], $('<div>'));

any matcher

Passing a parameter of $.jstub.any will create a wildcard match for a parameter:

$.stub(window, 'someFunction', [1, $.jstub.any, 'somethingElse'], 'was stubbed!');
someFunction(1, null, 'somethingElse); //will return 'was stubbed!'
someFunction(1, 213, 'somethingElse); //will return 'was stubbed!'
someFunction(1, new Object(), 'somethingElse); //will return 'was stubbed!'

Furthermore, you can match any parameters by specifying $.jstub.anyAll:

$.stub(window, 'someFunction', $.jstub.anyAll, 'was stubbed!');
someFunction(1, null, null); //will return 'was stubbed!'
someFunction(null, null, null); //will return 'was stubbed!'
someFunction({}, {}, {}); //will return 'was stubbed!'

single parameter

In the case where your method expects a single parameter (be it a simple value, or a more complex one), you do not have to pass the expected parameters in as an array:

$.stub($, 'post', {url: '/some/url', ...}, 'was stubbed!');

callbacks

Rather than having a stub return a value, you can make it invoke a callback from the original list of arguments. To do say the returnValue argument turns into the parameters to pass into the callback, and a new argument is added to specify the callback argument index. Think of the $.post and $.get jquery ajax method:

function doDelete(id)
{
  $.post('/url/delete', {id: id}, function(response, status)
    {
      $('tr[rel=' + response.deletedId + ']').remove();
    }, 'json');
}

In order to accurately stub our code we want to stub $.post yet make sure the callback is properly executed:

$.stub($, 'post', ['/url/delete', {id: 1}, $.jstub.any, 'json'], [1, 'ok'], 2);
doDelete(1);

ok($('tr[rel=1]').length == 0, "row was deleted");

In the above example the returnValue (the 4th argument to $.stub) will be passed to our callback. And the
callback that’ll be executed is the 2 (0-based) parameter of the original (unstubbed) call.

named callbacks

In some cases your callback will be embedded in an object literal – such as when you use the $.ajax method. Stubbing such a scenario requires one additional parameter – the name:

$.stub($, 'ajax', {url: '/url/delete', data:{id: 1}, success: $.jstub.any}, 'deleted response!!', 0, 'success');
doDelete(1);

failures

If a match cannot be found for a method which is being stubbed, an error will be thrown. If qunit is installed, a failed assertion with a error message will be displayed. If qunit is not installed, an exception will be raised.

resetting

All stubs can be reset by calling $.resetStubs()

expectations

jstub supports limited support for expectation checking. $.stub returns an object which has an invoked member which can be queried to count the number of times it was called:

var stub = $.stub($.blockUI, 'show', ['please wait'], null);
$.blockUI.show('please wait');
$.blockUI.show('something else');
$.blockUI.show('please wait');

The stub.invoked will be equal to 2

compatibility

jstub has been tested on IE 6, firefox 3.6 and Chrome 6.

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