If someone says a feature is not testable through the methods we use, it does not absolve us from the responsibility of testing; that's still our job. When this team was given a new connected device to test, they realized their existing functional testing skills wouldn't be sufficient to test the product's core algorithm. So the team got creative, learning the source code and introducing fault injection, figuring out new ways to test.
Since the completely random software fault insertion techniques suggested in much of the research literature are not practical for most software products, this paper suggests that a modest targeted software fault insertion effort for a few common error conditions can have a dramatic impact on defect detection rates and quality. The paper uses the example of a software fault insertion subsystem, codenamed Faulty Towers, which was added to Mangosoft Incorporated’s test automation in order to target
common failures and errors.