If the test specifications from the original development of the system are kept, one may be able to reuse them for regression testing and to adapt them for changes to the system. This may be as simple as changing the expected results for your existing tests. Sometimes additional tests may need to be built. Extension or enhancement to the system may mean new areas have been specified and tests would be drawn up just as for the development. It is also possible that updates are needed to an automated test set. which is often used to support regression testing.