Please empty your cache for these tests and make sure caching is on, if your dev tools are open.
preload
This section should contain 5 images of different file formats being preloaded on document ready.
After all images are preloaded, they should dynamically be placed here without triggering another
request, but getting the corresponding image directly from cache. Between load and display there is a
two second pause, so you can track the network activity in your dev tools showing, that the images are
not loaded the moment they are displayed, but way before.
loaded
On reload this section should load six images.
The first two are normal image loads of a standard image and a picture element (with picturefill).
The following two images are the same images again, which should now be delivered from cache,
but should fire their callbacks nonetheless.
Additionally, at last we add the same images again, wait until they are definitively loaded and
ready on the page and then set the load handler to see if the callback still fires.
So, in essence you should see six images (two different images), all being opaque after around two
seconds, having a green border to indicate the load event has fired.