# A UML Activity Flow Graph-Based Regression Testing Approach
## 2 Our Testing Approach
### UML Testing Approach  
To better understand regression testing for UML designs, it is important to first briefly discuss the UML testing technique. This technique involves creating an integrated model using class diagrams, sequence diagrams, and activity diagrams as the foundation for testing UML designs. An activity diagram provides a visual representation of the system's activities and the sequence in which they occur. By examining the diagram, testers can identify the different scenarios that the system may encounter during its operation. To generate regression test cases from an activity diagram, testers must first analyze the diagram to identify the possible paths the system may take. Testers should examine the different actions that occur during each step and determine the inputs and outputs that the system produces. They should also consider any conditional statements or loops that may affect the system's behavior. Once testers have identified the possible paths and actions, they can begin creating test cases. Each test case should target a specific path or action and should include the necessary inputs to trigger that action. Testers should also specify the expected outputs for each test case. To ensure thorough testing, testers should create test cases that cover all possible paths through the activity diagram. They should also consider any error conditions that may arise and create test cases to verify that the system handlesthese conditions properly. After creating the test cases, testers can execute them to verify that the system behaves as expected. They should record the results of each test case and any defects that are discovered. Any defects should be reported to the development team, who can then fix the issues and rerun the regression test cases to verify that the fixes have been successful.  
Creating an activity diagram from a sequence diagram is the first step. The activity diagram is mapped to an activity flow graph (AFG) in the second step. To create the Activity Flow Graph (AFG), the vertices and arcs of a directed acyclic graph are mapped from the object and sequence method calls present in an Activity Diagram. The relationships in the Sequence Diagram and the Activity Diagrams are preserved by the mapping between them. The mapping process entails two steps: (1) linking activity diagram methods to the objects from which they originated, and (2) traversing the diagram to map subsequent method executions to its edges. These edges are also marked with any restrictions that the Activity Diagram might place on how they should be used. Combining each AFG with the various pieces of information is the third step. A modified Activity Flow Graph is the result of this (AFG). The integrated model that unifies Activity Diagrams and Sequence Diagrams I now represented by the AFG.  
For every test case, \(T\), in an activity diagram, \(A_{D}\), we can construct a corresponding path, \(P_{T}\) as an execution path from the starting activity state to the end activity state consisting of activities and transitions, i.e., \(\forall T\in T[x]\), \(P_{T}=a_{s1}\to t_{c1}\to a_{s2}\to t_{c2}\to\cdots\to t_{cm}\to a_{sm}\), where \(a_{i}\in A_{s}\), \(t\in T[x]\), \(a_{s1}\) is the initial state and \(a_{sm}\) is the final state. The collection of test cases is \(T[x]\) and with every test case in \(T[x]\) there is a corresponding path \(P_{T}\). To navigate the AFG, values from the test cases are used (symbolic execution). We can now formally define the test case which will be used to identify and classify existing test cases and generate new test cases.  
**Definition 3** (Test Cases).: _A test case \(T\) in a UML diagram is a set of attributes satisfying certain conditions for the vertices of the \(P_{T}\) in the AFG._