Test Driven Development (TDD) refers a software development process involving the repetition of a very short development cycle. In the development cycle, the Cryptex ruby on Rails developers writes an automated test case (initially failing). In the automated test case, our developer defines a desired improvement. The developer defines a new function. In the agile test driven development process the developers’ produces the minimum amount of code in order to pass the test. Later, the written code is restructured to acceptable standards. The designer of such type of coding practice is of the opinion that it inspires confidence, encourages simple designs.