Object-oriented frameworks require thorough testing as they are reused repeatedly in developing numerous applications. Moreover, frameworks must be retested each time they are adapted and extended for reuse. Frameworks, however, have properties that make it difficult to control and observe the testing of the parts that were modified or extended. This paper describes a scheme of encapsulating test support code as built-in test (BIT) components and embedding them into the hook classes of an object-oriented framework so that defects caused by the modification and extension of the framework can be detected effectively and efficiently through testing. The test components built into a framework in this way increase the testability of the framework by making it easy to control and observe the process of framework testing without incurring changes or intervention to the framework code.