Which white-box test design technique focuses on the life cycle of data as it moves through the program to identify unused or uninitialized variables?

• A. Control flow testing
• B. Data flow testing
• C. Branch testing
• D. Path testing

Answer: (B)

Data flow testing tracks how each variable is created, modified, and ultimately used as the program runs. It looks at the life cycle of data, using the definitions and uses (def-use) relationships to catch problems where a variable is used before it’s initialized or where a definition is never used at all.

This white-box technique targets the data’s journey through the code, so test cases are crafted to expose issues like a use-before-definition or a definition that goes unused later. That focus makes it the best fit for identifying unused or uninitialized variables, as opposed to techniques that primarily examine the control path or branching structure. Control flow testing checks the order of statements and branches; path testing aims to cover all possible execution paths. Data flow testing complements these by zeroing in on how data moves and is validated along the way.