What's a good way to reuse test code using Jasmine?

Here is an article by a guy at Pivotal Labs that goes into detail about how to wrap a describe call:

DRYing up Jasmine Specs with Shared Behavior

Snippet from the article that shows part of the wrapper function:

function sharedBehaviorForGameOf(context) {
  describe("(shared)", function() {
    var ball, game;
    beforeEach(function() {
      ball = context.ball;
      game = context.game;
    });
  });
}

I'm not sure how @starmer's solution works. As I mentioned in the comment, when I use his code, context is always undefined.

Instead what you have to do (as mentioned by @moefinley) is to pass in a reference to a constructor function instead. I've written a blog post that outlines this approach using an example. Here's the essence of it:

describe('service interface', function(){
    function createInstance(){
        return /* code to create a new service or pass in an existing reference */
    }

    executeSharedTests(createInstance);
});

function executeSharedTests(createInstanceFn){
    describe('when adding a new menu entry', function(){
        var subjectUnderTest;

        beforeEach(function(){
            //create an instance by invoking the constructor function
            subjectUnderTest = createInstanceFn();
        });

        it('should allow to add new menu entries', function(){
            /* assertion code here, verifying subjectUnderTest works properly */
        });
    });
}

There's a nice article on thoughbot's website: https://robots.thoughtbot.com/jasmine-and-shared-examples

Here's a brief sample:

appNamespace.jasmine.sharedExamples = {
  "rectangle": function() {
    it("has four sides", function() {
      expect(this.subject.sides).toEqual(4);
    });
  },
 };

And with some underscore functions to define itShouldBehaveLike

window.itShouldBehaveLike = function() {
  var exampleName      = _.first(arguments),
      exampleArguments = _.select(_.rest(arguments), function(arg) { return !_.isFunction(arg); }),
      innerBlock       = _.detect(arguments, function(arg) { return _.isFunction(arg); }),
      exampleGroup     = appNamespace.jasmine.sharedExamples[exampleName];

  if(exampleGroup) {
    return describe(exampleName, function() {
      exampleGroup.apply(this, exampleArguments);
      if(innerBlock) { innerBlock(); }
    });
  } else {
    return it("cannot find shared behavior: '" + exampleName + "'", function() {
      expect(false).toEqual(true);
    });
  }
};