Well of course, in the not too distant future, cells will be synthesises (and possibly it depends on what you mean by synthesised since novel types of cells have certainly been created).
But I don't really understand your point in relation to the testability of ID. Because we have not achieved the synthesis of a cell from atomic or molecular components, then this is a test for ID? If (when) such cells are synthesised then we have demonstrated that ID is not correct? Can you clarify how your statement relating to cell synthesis can be seen as being a test ?