This paper presents the use of mutation analysis as the main qualification technique for: - estimating and automatically enhancing a test set (using genetic algorithms), - qualifying and improving a component's contracts (that is the specification facet) - measuring the impact of contractable robust components on global system robustness and reliability. The methodology is based on an integrated design and test approach for OO software components. It is dedicated to design-by-contract, where the specification is systematically derived into executable assertions called contracts (invariant properties, pre/postconditions of methods). The testing-for-trust approach, using the mutation analysis, checks the consistency between specification, implementation and tests. It points out the tests lack of efficiency but also the lack of precision of the contracts. The feasibility of components validation by mutation analysis and its usefulness for test generation are studied as well as the robustness of trustable and self-testable components into an infected environment.