When I did the kata the simple test cases seemed to be missing. Might I suggest something like:

describe('functionality tests', function() {
  function example(a, b) {
    return a + b;
  }
  
  var cached = cache(example);
  
  it('should return correct results', function() {
    Test.assertEquals(cached('foo', 'bar'), 'foobar', 'The cache function returned incorrect results');
    Test.assertEquals(cached('foo', 'bar'), 'foobar', 'The cache function returned incorrect result when called twice');
    Test.assertEquals(cached('foo', 'baz'), 'foobaz', 'The cache function returned incorrect results');
  });
}

This got a little fancy. I used a trie like structure to cache results. This would allow me to store less data if there were many similiar function calls. I also wanted to optimize the hashing for arguments and considered storing primative values directly.

Solid! That is nicer. Thanks.