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What is different is the incremental iterative approach to building out the landscape. Also, in the structured model, you would attempt to define all the input and output values before any coding could be done. Not so with TDD. Instead, everything is done incrementally and iteratively. Even the identification of the tests.
Should I care about testing
Now if you're reading this then I'm assuming you have an interest in unit testing and delivering quality systems. Why have I used the term system and not software? It's because the principle of TDD can be applied to the development of software and infrastructure. But can we apply to the concepts of design and architecture? That's a little more complex as these artifacts are logical constructs that cannot be executed. Your architecture and designs are made manifest through your software and hardware.