In this section, we first discuss a few basic concepts that are extensively used in the context of regression testing.
In this section, we discuss a few important notations and concepts relevant to regression testing.
Retestable test cases are those test cases that execute the modified and the affected parts of the program and need to be rerun during regression testing.
The RTS techniques proposed in  select a test case t for regression testing only if the slice of t computed using any one of the four approaches contains a statement modified in P'.
However, the PDG-based slicing technique did not support inter-procedural regression testing.
Test cases that exercise any of the modified entities are selected for regression testing P'.
This creates a new dimension in regression testing of object-oriented programs that use these third-party components or libraries, since the source code for such libraries are often not available.
The following are some important advantages of UML-based regression testing :
Scalability--Code-based regression testing becomes very expensive when applied to large programs.
in  for regression testing based on UML design models by also including information available from class diagrams.
The paths in the diagram that have one or more modified nodes are considered to be affected and the test cases which execute the affected paths are selected for regression testing.
Hence, regression testing of component-based software needs to address how the changes made to a component might affect the execution of application programs which use those modified components.