Whitebox testing

SOFTWARE QUALITY
ASSURANCE
WHITE BOX

Seminar: Oana FEIDI
Quality Manager – Continental Automotive

BLACK-BOX VS. WHITE-BOX

 Test cases derived from specifications

 The focus is not the design, nor the implementation
 The focus is on the logic of implementation

WHITE BOX (STRUCTURAL
TESTING)
 Structural - test case selection is based on an
analysis of the internal structure of
component

 Control flow
 Statement testing

 Branch/Decision Testing

 Branch Condition Testing

 Modified Condition Combination Testing

 Data flow testing

WHITE BOX
 Using the white-box testing techniques outlined
in this seminar, a software engineer can design
test cases that
 exercise independent paths within a module or unit;
 exercise logical decisions on both their true and false side;

 execute loops at their boundaries and within their

operational bounds
 exercise internal data structures to ensure their validity

STATEMENT TESTING
 uses a model of the program’s control flow
 it is designed in order to execute all or selected statements of the
test object
Test cases are design to execute
each statement.
An entity in a programming
For each test case specify: language which is typically
the smallest indivisible unit of
• the input(s) of the component execution.

• identification of statement(s) to be
executed by the test case
• the expected outcome of the test
case
Test completeness criteria: the percentage of the statements in the
software which were executed at least at once (executing a statement
means that the statement was encountered and evaluated during testing).

EXAMPLE
float foo (int a, int b, int c, int d, float e)
{
float e;
if (a == 0) {
return 0;
}
int x = 0;
if ((a==b) OR ((c == d) AND bug(a) )) {
x=1;
}
e = 1/x;
statement
return e;
}

BRANCH/DECISION TESTING
 uses a model of the program’s flow
 it is designed in order to execute (each) outcome
of all or selected decision points in a test object
an executable statement
For each test specify:
which may transfer control
• the input(s) of the component to another statement,
depending upon the logic
• Identification of decision
of the decision statement
outcome(s) to be executed by
the test case
• the expected outcome of the
test case

Test completeness criteria: achievement of the test coverage – 100%
of the branches (one true and one false for each part of condition)

EXAMPLE
A = true and (B or C) = false
 A = false and (B or C) = true

if A and (B or C)

Case A B C Output

1 0 1 1 0

2 1 0 0 0

BRANCH CONDITION COMBINATION
 uses a model of the program flow where each
combination of the inputs for a decision/condition must
be tested, in order to check if each branch is covered
 For each test case specify:
 the input(s) of the component
 the expected outcome of the test case which can show which

branch is covered

Test completeness criteria: for a condition containing n
boolean operands → 2n test cases are required to achieve
100% coverage
Note: this coverage rapidly becomes unachievable for more
complex conditions.

WHITE BOX - SUMMARY
 Statement testing
 uses a model of the program’s control flow
 it is designed in order to execute all or selected statements of

the test object
 Branch/Decision Testing
 uses a model of the program’s flow
 it is designed in order to execute (each) outcome of all or

selected decision points in a test object
 Branch Condition Combination
 uses a model of the program flow where each combination
of the inputs for a decision/condition must be tested, in
order to check if each branch is covered

MODIFIED CONDITION COMBINATION
TESTING
 usesa model of the program’s flow where each
atomic condition is independently tested, in order
to show how the decision outcome is affected

 test
case are designed to show that each condition
independently affects the decision outcome

 For each test case specify:
 the input(s) of the component
 The expected outcome of the test case

MODIFIED CONDITION COMBINATION
TESTING
 Test completeness criteria
 for a condition containing n boolean operands, to achieve
100% coverage are necessary:
 minimum: n + 1 test cases
 maximum: 2n test cases

 Example: for 3 boolean operands, to achieve 100%
coverage are necessary:
 Minimum 4 test cases
 Maximum 6 test cases

EXAMPLE
Case A B B or C C Outcome

1 1 1 1 0 1 if (A and (B or C))

2 0 0

3 1 1 1 0 1

4 0 0 0

5 1 0 1 1 1

6 0 0 0

LOOP TESTING
 Simple Loops:- 'n' is the maximum number of allowable
passes
 skip the loop entirely.
 only one pass thru the loop.

 two passes thru the loop.

 m passes thru the loop where m< n.

 n-1,n,n+1 passes thru the loop

 Nested loops
 start with the innermost loop. Set all other loop to min. values.
 conduct simple loop tests for the innermost loop while holding the
outer loops at their min. iteration values.
 work outward, conducting tests for the next loop, but keeping all
the outer loops at their min. iteration count.
 continue until all loops have been tested.

EXERCISE
 1) Identify what scenarios have to be run to achieve
100% statement coverage and 100% branch coverage
on the following code

 2) Test the same examples on the following link.
Does white-box covers 100% the black-box?

Whitebox testing

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