What do you mean by &quot;testable&quot;? There&#x27;s a pretty big spectrum of &quot;untestable&quot; ranging from requiring too many trillions of dollars to requiring more resources than this planet has to requiring equipment or energy levels we don&#x27;t know how to produce even in theory to requiring stuff we&#x27;re pretty sure is impossible like looking beyond the range of the observable universe or requiring more energy than is contained in the observable universe.<p>And at what point in its development and study do you abandon a theory that nobody has yet invented a way to test?