We present a new, automatic technique to assess whether replacing a component of a software system by a purportedly compatible component may change the behavior of the system. The technique operates before integrating the new component into the system or running system tests, permitting quicker and cheaper identification of problems. It takes into account the system's use of the component, because a particular component upgrade may be desirable in one context but undesirable in another. No formal specifications are required, permitting detection of problems due either to errors in the component or to errors in the system. Both external and internal behaviors can be compared, enabling detection of problems that are not immediately reflected in the output.The technique generates an operational abstraction for the old component in the context of the system and generates an operational abstraction for the new component in the context of its test suite; an operational abstraction is a set of program properties that generalizes over observed run-time behavior. If automated logical comparison indicates that the new component does not make all the guarantees that the old one did, then the upgrade may affect system behavior and should not be performed without further scrutiny. In case studies, the technique identified several incompatibilities among software components.