&gt; That may be, but it ignores the fact that software was written for the express purpose of not just identifying if a test was being ran, but then taking action to change the results of the test has no real world use.<p>I think it depends on how general the implementation was.  I could imagine real world uses for a feature to generically detect certain conditions and change parameters in response (e.g. to support different settings for highway vs city driving).  If you have something general enough, then the &quot;defeat device&quot; could have just been a ruleset that only matched a very narrow set of conditions that usually only occurs during the tests.