Yes: TDD is mainly a good design technique (and only secondary a testing technique). It helps very much to achieve the solid principles, though (pathological) examples of TDD with a lot of code smells are still possible.
The connection between TDD and the solid principles are disputed (with the conclusion above) in this great hanselminute podcast named "TDD is design"this great hanselminute podcast named "Test Driven Development is Design - The Last Word on TDD".