Lecture 4-Mutation Testing

Question 1

What is mutation testing and what does it do?

Answer 1

-It’s a fault-based testing: directed towards typical faults that could occur in a program.
-Modify (MUTATE) some statements in the code, so we have many different versions of the code. EACH VERSION IS A BUG.

Question 2

How do we know if the mutant Is killed or alive ?

Answer 2

-Mutant is killed if: different results are found, the test case is good as it detects the change.
-Mutant is alive if: the results are the same. test is NOT effective.

Question 3

What are the two reasons why a mutant remains live?

Answer 3

• It’s equivalent to the original program
  -The test case is inadequate to kill the mutant

Question 4

How should mutation testing be used?

Answer 4

In conjunction with traditional testing techniques, NOT INSTEAD OF THEM.

Question 5

What are mutation operators used for?

Answer 5

For the automated generation of mutants

Question 6

What are 3 examples of mutants?

Answer 6

Stillborn mutant: syntactically incorrect, killed by compiler
Trivial mutant: killed by almost any test case
-Equivalent mutant: always produces the same output as the original program

Question 7

What is the competent programmer assumption?

Answer 7

A programmer develops a program that is either correct or differs from the correct program by a combination of simple errors.

Question 8

What is the coupling effect assumption?

Answer 8

Complex faults are coupled to simple faults in such a way that a test data set that detects all simple faults in a program will detect a high percentage of the complex faults.

Question 9

What is complete coverage in mutation coverage ?

Answer 9

It equates to killing ALL non-equivalent mutants

Question 10

What is mutation score?

Answer 10

-The amount of coverage
-Ratio of dead mutants over all non-equivalent mutants:
100 * dead mutants/(number of mutants - equivalent mutants)
-A set of test cases is mutation adequate if its mutation score is 100%
-NUMBER OF MUTANTS TENDS TO BE LARGE EVEN FOR SMALL PROGRAMS

Question 11

Strong vs weak mutation

Answer 11

Strong:
-A fault must be reachable
-Infect the state
-Propagate to output
Weak:
-A fault must be reachable
-Infect the state
* They require almost the same number of test cases to satisfy them

Question 12

Define strongly killing mutants

Answer 12

If: m is mutant, p is program and t is test case:
it is said to strongly kill m if the output of t/p is different from t/m.

Question 13

What is strong mutation coverage (SMC) ?

Answer 13

For each mutant m in M, TR contain a test case which strongly kills m.

Question 14

Define weakly killing mutants

Answer 14

If : m is mutant , l is source location, p is program and t is test :
t is said to weakly kill m if the STATE of the execution of p/t is different from the STATE of execution of m/t, immediately after some execution of L.

Question 15

What is weak mutation coverage (WMC)?

Answer 15

For each mutant m in M, TR contains a test case which weakly kills m.