Contract driven development = test driven development - writing test cases

Although unit tests are recognized as an important tool in software development, programmers prefer to write code, rather than unit tests. Despite the emergence of tools like JUnit which automate part of the process, unit testing remains a time-consuming, resource-intensive, and not particularly appealing activity.This paper introduces a new development method, called Contract Driven Development. This development method is based on a novel mechanism that extracts test cases from failure-producing runs that the programmers trigger. It exploits actions that developers perform anyway as part of their normal process of writing code. Thus, it takes the task of writing unit tests off the developers' shoulders, while still taking advantage of their knowledge of the intended semantics and structure of the code. The approach is based on the presence of contracts in code, which act as the oracle of the test cases. The test cases are extracted completely automatically, are run in the background, and can easily be maintained over versions. The tool implementing this methodology is called Cdd and is available both in binary and in source form.