1.
Whitebox Testing

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Today’s topic

3. Recall: Common approaches for choosing test cases
Blackbox testing: Choose based on module’s possible inputs and outputs
Do not use code
Often test boundary cases
White-box testing: Uses internal logic to choose tests
Different levels of code coverage
Aka glass box testing, clear box testing
Regression testing: Keep tests that reveal old bugs
Rationale: “Fixed” bugs come back!

4. Criteria for choosing test cases: Coverage Measures
Degree to which the source code of a program is tested by a test suite
Examples:
Statement coverage
Condition coverage
Path coverage
Some examples will clarify, but first…

5. Control Flow Graphs – Frequently used to calculate coverage
int foo(int x, int y) {
int z = 0;
if ((x>0) && (y>0)) {
z = x; }
return z;
Basic blocks: straight-line pieces of code without any jumps or jump targets
return z;
z = x;
int z = 0;
if ((x>0) && (y>0)) {
true
false
Jumps: control branches

6. Statement Coverage
Set of test cases such that… Each program statement (line or basic block) is executed at least once

7. Define a test suite that provides statement coverage for this code
return z;
z = x;
int z = 0;
if ((x>0) && (y>0)) {
true
false
Control Flow Graph
int foo(int x, int y) {
int z = 0;
if ((x>0) && (y>0)) {
z = x; }
return z; ✔ ✔
input
expected x y ✔ 1

8. Now try this code… Control Flow Graph F T T F T F
public int bar(int x) {
int result=0;
if (x < 69) {
if (x % 2 == 0) {
result = x/2;
} else {
result = x*2; }
} else if (x > 6969) {
x = 69;
x = 6969;
return result;
Control Flow Graph
int result=0;
result = x*2; F T
x < 69
x % 2 == 0 T F
result = x/2; T
x > 6969
x = 69; F
return result;
x = 6969;

9. ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970
Control Flow Graph 70
6969 ✔ ✔
int result=0;
result = x*2; ✔ ✔ F T
x < 69
x % 2 == 0 T ✔ F
result = x/2; ✔ ✔ T
x > 6969
x = 69; ✔ F
return result; ✔
x = 6969;

10. Condition Coverage
Set of test cases such that… Each boolean expression (in control structures) evaluates to true at least once and to false at least once

11. ✔ ✔ Define a test suite that provides condition coverage for this code
return z;
z = x;
int z = 0;
if ((x>0) && (y>0)) {
true
false
Control Flow Graph
int foo(int x, int y) {
int z = 0;
if ((x>0) && (y>0)) {
z = x; }
return z; ✔ ✔
input
expected x y 1

12. Now try this code… Control Flow Graph F T T F T F
public int bar(int x) {
int result=0;
if (x < 69) {
if (x % 2 == 0) {
result = x/2;
} else {
result = x*2; }
} else if (x > 6969) {
x = 69;
x = 6969;
return result;
Control Flow Graph
int result=0;
result = x*2; F T
x < 69
x % 2 == 0 T F
result = x/2; T
x > 6969
x = 69; F
return result;
x = 6969;

13. ✔ ✔ ✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970 69
Control Flow Graph 70
6969
int result=0;
result = x*2; ✔ ✔ F T
x < 69
x % 2 == 0 ✔ T ✔ F
result = x/2; ✔ T
x > 6969
x = 69; ✔ F
return result;
x = 6969;

14. Path Coverage
Set of test cases such that… Each possible path through a program’s control flow graph is taken at least once

15. ✔ ✔ Define a test suite that provides path coverage for this code
return z;
z = x;
int z = 0;
if ((x>0) && (y>0)) {
true
false
Control Flow Graph
int foo(int x, int y) {
int z = 0;
if ((x>0) && (y>0)) {
z = x; }
return z;
(a)
(b)
(c)
input
expected x y 1
Paths:
a , b c ✔ ✔

16. Now try this code… Control Flow Graph F T T F T F
public int bar(int x) {
int result=0;
if (x < 69) {
if (x % 2 == 0) {
result = x/2;
} else {
result = x*2; }
} else if (x > 6969) {
x = 69;
x = 6969;
return result;
Control Flow Graph
int result=0;
result = x*2; F T
x < 69
x % 2 == 0 T F
result = x/2; T
x > 6969
x = 69; F
return result;
x = 6969;

17. ✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970 69 70 6969
Control Flow Graph
int result=0;
(a)
(b)
(c)
(d)
(f)
(e)
(g)
(h)
(i)
(j)
(k)
result = x*2; F T
x < 69
Paths:
a , d , f , h
a , d , g , i
a , b , e , j
a , b , c , k
x % 2 == 0 ✔ T ✔ F
result = x/2; ✔ ✔ T
x > 6969
x = 69; F
return result;
x = 6969;

18. BONUS QUESTION

19. Draw a control flow graph Define test suites that provide:
Given this code
Draw a control flow graph
Define test suites that provide:
Statement coverage
Condition coverage
Path coverage
int myF(int x, int y) {
while (x > 10) {
x = x – 10;
if (x == 10) {
break; }
if (y < 20 && x%2 == 0) {
y = y + 20;
} else {
y = y – 20;
return 2*x + y;

20. Here’s the CFG F T F T F T int myF(int x, int y) { while (x > 10) {
x = x – 10;
if (x == 10) {
break; }
if (y < 20 && x%2 == 0) {
y = y + 20;
} else {
y = y – 20;
return 2*x + y;
while (x > 10) F T
x = x – 10;
if (x == 10) F T
break;
if (y < 20 && x%2 == 0) F T
y = y – 20;
y = y + 20;
Here’s the CFG
return 2*x + y;