How do I test a new theme with sample products without them showing in my live theme?

[WayneH]

I have a store running with a custom theme, but would like to build a new design in the background using a different standard theme. The reason I'm developing the new store is because we are going to expand into several new product categories (so, new collections). I added these new products and collections, but in order to see them in my development theme I have to turn them on, which makes them visible on the live site, which I do not want because they are not ready for sale yet.  Is there a combination of settings somehow to make them active in the test theme without appearing in the live theme?

I appreciate any help!!!