Regression testing is a
process, which tests a system once again to ensure that it still functions as
expected / as per specifications or its requirements. In brief we can say
Regression testing as verification of a bug when it has been fixed
(Note1) for example, If a bug is
fixed in a module called “User” and if that bug has an impact on the other
module called “report” then execute all the test cases of both modules to
ensure that Functionality remains same
(Note2) if a module has 50 test cases and
only one test case found to be failed and same has been logged as a bug, when
it fixed and reverts back for verification you have to
Execute
all the 50 cases.