I would agree with what you said if you replaced "an application" with "a kind of application". This is a 10MLoC project that was mostly not written for unit te

I would agree with what you said if you replaced "an application" with "a kind of application". This is a 10MLoC project that was mostly not written for unit testablility. As stated in the article, they are doing automatic integration testing on a functional level to catch regressions. They are enforcing zero warnings and run static analysis software. And most importantly, their code has worked in the field for a long time. I strongly suspect that refactoring for unit testability would be a very significant risk in their case. The quote does not say that they don't unit-test new code.