I'm not sure they became instantly test-driven, but I do think that the exception handling model as default error handling in Java and C# was a big drive toward

I'm not sure they became instantly test-driven, but I do think that the exception handling model as default error handling in Java and C# was a big drive toward test-driven development. Eventhough both have the ability to do runtime assertions and even work with contracts to some degree. It's also why I think Go's panic is far preferable, but that's a different story, and Go doesn't have runtime assertions so there is that. But it was probably more than just type systems and error handling. What it has meant, at least in my part of the world, is that a lot of programmers (and I mean the vast majority) are very bad at deal with errors exactly when they happen. This is anecdotal, but I think I've met one or two developers outside the telecom and energy sectors that knew you could do runtime assertions.