Chapter 06: Mutation Testing

Question 1

One advantage of coverage criteria

Answer 1

can be measured automatically

Question 2

When to stop testing?

Answer 2

Cumulative number of failures found so far have a “saturation effect”

Question 3

2 Types of Test critera

Answer 3

1. Coverage based: covers most specification
2. Fault-based: finds most bugs

Question 4

Definition: Mutation Testing

Answer 4

“fault based testing”

intentionally create small, syntactic changes in the code (called mutants) to simulate common mistakes.

Ex: x = a + b ➝ x = a - b

Question 5

Different types of mutants?

Answer 5

Stillborn: syntactically incorrect and killed by compiler

trivial: killed by any test case

equivalent mutant: acts the same behavior as the oirignal program (CANNOT BE KILLED)

Question 6

Killed vs. Alive mutants

Answer 6

If the same test cases can detect differences between a mutant and the original code then the mutant is killed.

Question 7

Examples of Method-Level Mutatons?

Answer 7

1. variable replacement
2. relational operator replacement
3. off-by-1
4. replacement by 0
5. arithmetic operator replacement

Question 8

Examples of Class-Level Mutations?

Answer 8

1. Access modifier change
2. type cast change
3. super keyword insertion
4. method calling position change

Question 9

How to calculate Mutation score?

Answer 9

Score = # of mutants killed / # of NON-equivalent mutants