Software-based applications with high reliability demands require extensive verification and validation activities capable of providing significant evidence for the achievement of the reliability degree required. For the purpose of exposing interaction faults, extensive integration testing phases are recommended. In order to support them the article proposes appropriate interaction coverage concepts and automatic test case generation techniques. With regard to reliability assessment, the article presents an approach to enhance the sharpness of system reliability statements based on the integration of statistical samples concerning component testing resp. operating experience.