JNTU MCA 2019 SOFTWARE TESTING METHODOLOGIES Previous Question Paper (April/May - 2019 - R15)

A Control Flow Graph (CFG) is a directed graph representation of all paths that might be traversed through a program during its execution. In a CFG, nodes represent basic blocks of code (sequences of instructions with one entry and one exit point), and edges represent the flow of control between these blocks, such as branches, loops, or sequential execution.

The independence and correlation of variables and predicates are defined as follows:

• Independence: Variables or predicates are considered independent if the value of one does not affect the value or outcome of the other. In testing, independent variables allow for partitioning the input space without considering the state of other variables, simplifying path analysis.
• Correlation: Variables or predicates are correlated if they are linked through program logic, such that the value of one variable constrains or determines the value of another. Predicates are correlated if the truth value of one predicate influences the probability or possibility of another predicate being true or false.

Understanding these relationships is critical for path testing, as correlated variables can lead to infeasible paths where certain combinations of conditions can never be satisfied simultaneously.

In Transaction Flow Testing, births and mergers are critical structural elements used to model the lifecycle and concurrency of transactions within a system.

A birth occurs when a transaction is created or initiated. It represents the point in the flow where a new transaction instance enters the system, often triggered by an external event, a user input, or as a result of a previous transaction processing step. In a flow graph, this is typically represented by a node with an out-degree greater than zero and an in-degree of zero, signifying the origin of the transaction path.

A merger occurs when two or more independent transaction paths or sub-flows converge into a single path. This represents the point where different processing branches combine to continue execution as a unified flow. In a flow graph, a merger is represented by a node with an in-degree greater than one. Mergers are essential for identifying synchronization points, shared resources, or common processing logic that must handle inputs from multiple preceding states.

Understanding these elements is vital for test design, as they help identify potential bottlenecks, race conditions, and synchronization errors. Testers focus on these points to ensure that transaction integrity is maintained during creation and that all converging paths are correctly handled without data loss or state corruption.