[rswail]

Source code control has been around since SCCS in the early 80s (although wikipedia says 1977), it begat RCS which begat CVS, which begat SVN.

People have been using source code control since then, but the history of computing is of wheel reinvention and not-invented-here, so we are condemned to rediscover things.

Unit testing is useful for business logic, not for individual functions. If you're writing unit tests around whether or not you go outside an array bound, then you're testing the wrong thing. If, on the other hand, you're making sure that someone under 13 can't signup for a service, that's a reasonable unit test.

DI can be useful for running code, allowing you to instrument the code to identify problems. But that's runtime DI, not compile/deployment time.

As a design pattern, it's more an abstraction / reduction of general parameterized polymorphism, usually dragging in an opinionated framework that requires you to follow a set pattern of development and deployment.