Regarding testability, ID makes the following testable predictions:
(1) Natural structures will be found that contain many parts arranged in intricate patterns that perform a specific function (e.g. complex and specified information).
(2) Forms containing large amounts of novel information will appear in the fossil record suddenly and without similar precursors.
(3) Convergence will occur routinely. That is, genes and other functional parts will be re-used in different and unrelated organisms.
(4) Much so-called “junk DNA” will turn out to perform valuable functions.
In this regard, ID is falsifiable. When we test these predictions, ID passes those tests.
And here’s some detail on 3), because I’ve never talked about convergence on the blog:
Regarding prediction 3, similar parts have been found in organisms that even Darwinists see as separated by more closely related forms that do not contain the similar parts in question. Clear examples include genes controlling eye or limb growth in different organisms whose alleged common ancestors are not thought to have had such forms of eyes or limbs. For details, please see: A Primer on the Tree of Life.
An example would be where humans and octopi have the same kind of eyes, but they don’t share a common ancestor. So the designed “evolved” in two places independently. A simpler explanation that something so unlikely is that the two systems have a common designer.
The article lists several scientific areas where ID has explanatory power.