We describe next the two types of testing—developmental and operational testing—that take place during the development process. Developmental testing includes testing of components, subsystems, and software to ensure that performance capability and reliability are designed into the system early. Developmental testing then proceeds to system-level and system-of-systems–level testing to ensure that the system has matured to the point at which it can be expected to meet initial operational test and evaluation and operational employment requirements. Operational testing is a test of the full production representative system in as operationally realistic a setting as possible, with representation of opposition forces, countermeasures, and participation by users with training equivalent to what would be available in the field under circumstances of typical use.
These two types of defense testing have different objectives. Developmental testing is used to determine the capabilities of components and of the full system against individual stress factors, to help identify failure modes. The intent is to discover changes that can greatly improve the overall design. In addition, developmental testing is intended to help produce a system that would be expected to pass operational testing in proceeding to full-rate production. To examine whether a system design is mature, it is vital to learn about the performance of each component and, to some extent, their interactions. Therefore, during developmental testing, testing under more strenuous circumstances, that is, testing at the edge of the envelope, may be conducted.