What is "tdd"

Test Driven Development (TDD) or in Portuguese Development Directed by Tests is a software development technique that is based on a short cycle of repetitions:

First the developer writes an automated test case that defines a desired improvement or new functionality. Then, code is produced that can be validated by the test for later code to be refactored to a code under acceptable standards.

Kent Beck, considered the creator or 'discoverer' of the technique, stated in 2003 that TDD encourages simple code designs and inspires confidence. The test-driven development is related to Extreme Programming programming concepts, started in 1999, but recently has created greater interest in it due to its own ideals. Through TDD, programmers can apply the concept of improving and debugging legacy code developed from old techniques.

For more information, visit: Test Driven Development.