Both Unit testing and Design by Contract are valuable test approaches in my experince.
I have tried using Design by Contract in a System Automatic Testing framework and my experience is that is gives a flexibility and possibilities not easily obtained by unit testing. For example its possible to run longer sequence and verify that
the respons times are within limits every time an action is executed.
Looking at the presentations at InfoQ it appears that Design by contract is a valuable addition to the conventional Unit tests in the integration phase of components.
For example it possible to create a mock interface first and then use the component after-
or when a new version of a component is released.
I have not found a toolkit covering all my design requirement to design by contract testing
in the .Net/Microsoft platform.
