Part 2: W09-1 Testing Structure

Question 1

What are the type of data-flow anomalies?

Answer 1

1. Defined and then redefined.
2. Undefined and then referenced.
3. Defined and not referenced.

Question 2

What can be used to explore data-flow anomalies?

Answer 2

Control Flow Graph (CFG)

Question 3

How can data-flow anomalies be discovered using CFG?

Answer 3

Go through CFG and at each node label which variables are defined and which variables are used (predicate and computation use)

Then use above information to look at Du-paths and Dc-paths

Question 4

What is a Du-path?

Answer 4

• Path in Data Flow Graph
• Definition-use subpath with respect to some variable
• can have multiple defiinitions

Question 5

What is a Dc-path?

Answer 5

• Path in Data Flow Graph
• Definition-clear subpath with respect to some variable
• can only have one definition node