"Refreshing" for debugging

If I add a development version of an epub3 book from a local file to Readium (in Chrome) I can read it immediately. If I see a problem with it, I can quickly fix it at source and create a new epub file. However, I can't find a way to tell Readium to use the updated version, even though I've closed the fresh tab it automatically opened. Currently I have to click Details, select Delete, then click the library button and add the book once more from my local file.

This isn't much of a problem, but given the number of mistakes I make developing a complex ebook, is there a way to simply tell Readium to refresh the source?

Or, to put it another way, where is Readium reading my ebook from when I click to open it? Is it creating a local cached version?

Thanks, as always, to the idpf who are making epub3 a real marvel!

Steven