Software Testing Methodology Question:

Background " One segment of system is developed and thoroughly tested.
" Another segment is changed which has disastrous effect on the tested segment.
" The implemented change, new data or parameters have created change in the already tested segment.
Usage " All aspects of system remain functional after testing.
" Change in one segment does not change the functionality of other segment.
Objectives " Determine -
system documents remain current
System test data and test conditions remain current.
Previously tested system functions properly without getting effected though changes are made in some other segment of application system.
How to Use " Test cases, which were used previously for the already tested segment is, re-run to ensure that the results of the segment tested currently and the results of same segment tested earlier are same.
" Test automation is needed to carry out the test transactions (test condition execution) else the process is very time consuming and tedious.
" In this case of testing cost/benefit should be carefully evaluated else the efforts spend on testing would be more and payback would be minimum.
When to use " When there is high risk that the new changes may effect the unchanged areas of application system.
" In development process: Regression testing should be carried out after the pre-determined changes are incorporated in the application system.
" In Maintenance phase : regression testing should be carried out if there is a high risk that loss may occur when the changes are made to the system
Examples " Re-running of previously conducted tests to ensure that the unchanged portion of system functions properly.
" Reviewing previously prepared system documents (manuals) to ensure that they do not get effected after changes are made to the application system.
" Obtaining printout of data dictionary to ensure that the data elements reflect the changes being incorporated.
Disadvantage " Time consuming and tedious if test automation not done.