1. Software Verification
Graph Model 2

2. Model-Driven Test Design – Activities
refined requirements / test specs
Test Design
model / structure
test requirements
DESIGN
ABSTRACTION
LEVEL
IMPLEMENTATION
ABSTRACTION
LEVEL
software artifact
input values
Test Automation
Test Evaluation
pass / fail
test results
Test Execution
test scripts
test cases

3. Embed test values into executable scripts
2. Test Automation
Embed test values into executable scripts
This is slightly less technical
Requires knowledge of programming
Fairly straightforward programming – small pieces and simple algorithms
Programming is out of reach for many domain experts

4. 3. Test Execution 4. Test Evaluation
Run tests on the software and record the results
This is easy – and trivial if the tests are well automated
4. Test Evaluation
Evaluate results of testing, report to developers
This is much harder than it may seem

5. Testing : Finding inputs that cause the software to fail
Testing & Debugging
Testing : Finding inputs that cause the software to fail
Debugging : The process of finding a fault given a failure

6. Static and Dynamic Testing
Static Testing : Testing without executing the program
This include software inspections and some forms of analyses
Very effective at finding certain kinds of problems – especially “potential” faults, that is, problems that could lead to faults when the program is modified
Dynamic Testing : Testing by executing the program with real inputs

7. Stress testing
Exercises the system beyond its maximum design load. Stressing the system often causes defects to come to light
Stressing the system test faulure behaviour.. Systems should not fail catastrophically. Stress testing checks for unacceptable loss of service or data
Particularly relevant to distributed systems which can exhibit severe degradation as a network becomes overloaded

8. Tests that are at the limit of the software’s expected input domain
Stress Testing
Tests that are at the limit of the software’s expected input domain
Very large numeric values (or very small)
Very long strings, empty strings
Null references
Very large files
Many users making requests at the same time
Invalid values

9. Back-to-back testing
Present the same tests to different versions of the system and compare outputs. Differing outputs imply potential problems
Reduces the costs of examining test results. Automatic comparison of outputs.
Possible to when a prototype is available or with regression testing of a new system version

10. Performance testing Does it meet requirements?
Test for performance behavior
Does it meet requirements?
Customer requirements
Definitional requirements (e.g. Ethernet)
Test for resource utilization
Understand resource requirements
Test performance early
Avoid costly redesign to meet performance requirements

11. Security Testing Example: denial of service Example: network topology
Is data/access safe from those who should not have it?
Is data/access available to those who should have it?
How is privilege granted/revoked?
Is the system safe from unauthorized control?
Example: denial of service
Collateral data that compromises security
Example: network topology

12. Test Case
Test Case Values : The values that directly satisfy one test requirement
Expected Results : The result that will be produced when executing the test if the program satisfies it intended behavior

13. Models for Quality in Software
CMMI-SW
ISO 9001:2000
ISO 90003
TickIt
Six Sigma
Plan, Do, Check, Act (PCDA)

14. Data Flow Test Criteria
First, we make sure every def reaches a use
All-defs coverage (ADC) : For each set of du-paths S = du (n, v), TR contains at least one path d in S.
Then we make sure that every def reaches all possible uses
All-uses coverage (AUC) : For each set of du-paths to uses S = du (ni, nj, v), TR contains at least one path d in S.
Finally, we cover all the paths between defs and uses
All-du-paths coverage (ADUPC) : For each set S = du (ni, nj, v), TR contains every path d in S.

15. Data Flow Testing Example2 1 6 3 5 4
X = 42
Z = X-8
Z = X*2
All-defs for X
[ 0, 1, 3, 4 ]
All-uses for X
[ 0, 1, 3, 4 ]
[ 0, 1, 3, 5 ]
All-du-paths for X
[ 0, 1, 3, 4 ]
[ 0, 2, 3, 4 ]
[ 0, 1, 3, 5 ]
[ 0, 2, 3, 5 ]

16. Example: Definition and Uses
What are the definitions and uses for the program below?
1. read (x, y);
2. z = x + 2;
3. if (z < y)
4 w = x + 1;
else
5. y = y + 1;
6. print (x, y, w, z);

17. Example: Definition and Uses
x, y z x
z, y w y
x, y, w, z
1. read (x, y);
2. z = x + 2;
3. if (z < y)
4 w = x + 1;
else
y = y + 1;
6. print (x, y, w, z);

18. Example Data Flow – Stats
public static void computeStats (int [ ] numbers) {
int length = numbers.length;
double med, var, sd, mean, sum, varsum;
sum = 0.0;
for (int i = 0; i < length; i++)
sum += numbers [ i ]; }
med = numbers [ length / 2 ];
mean = sum / (double) length;
varsum = 0.o;
varsum = varsum + ((numbers [ i ] - mean) * (numbers [ i ] - mean));
var = varsum / ( length - 1 );
sd = Math.sqrt ( var );
System.out.println ("length: " + length);
System.out.println ("mean: " + mean);
System.out.println ("median: " + med);
System.out.println ("variance: " + var);
System.out.println ("standard deviation: " + sd);

19. Control Flow Graph for Stats
public static void computeStats (int [ ] numbers) {
int length = numbers.length;
double med, var, sd, mean, sum, varsum;
sum = 0.0;
for (int i = 0; i < length; i++)
sum += numbers [ i ]; }
med = numbers [ length / 2 ];
mean = sum / (double) length;
varsum = 0.o;
varsum = varsum + ((numbers [ i ] - mean) * (numbers [ i ] - mean));
var = varsum / ( length - 1 );
sd = Math.sqrt ( var );
System.out.println ("length: " + length);
System.out.println ("mean: " + mean);
System.out.println ("median: " + med);
System.out.println ("variance: " + var);
System.out.println ("standard deviation: " + sd); 8 1 2 4 3 5 6 7
( numbers )
sum = 0
length = numbers.length
i = 0
i >= length
i < length
med = numbers [ length / 2 ]
mean = sum / (double) length
varsum = 0
i = 0
sum += numbers [ i ]
i++
i >= length
i < length
var = varsum / ( length )
sd = Math.sqrt ( var )
print (length, mean, med, var, sd)
varsum = …
i++

20. CFG for Stats – With Defs & Uses8 1 2 4 3 5 6 7
def (1) = { numbers, sum, length }
def (2) = { i }
use (3, 5) = { i, length }
use (3, 4) = { i, length }
def (5) = { med, mean, varsum, i }
use (5) = { numbers, length, sum }
def (4) = { sum, i }
use (4) = { sum, numbers, i }
use (6, 8) = { i, length }
use (6, 7) = { i, length }
def (8) = { var, sd }
use (8) = { varsum, length, mean,
med, var, sd }
def (7) = { varsum, i }
use (7) = { varsum, numbers, i, mean }

21. Defs and Uses Tables for Stats
Node
Def
Use 1
{ numbers, sum, length }
{ numbers } 2
{ i } 3 4
{ sum, i }
{ numbers, i, sum } 5
{ med, mean, varsum, i }
{ numbers, length, sum } 6 7
{ varsum, i }
{ varsum, numbers, i, mean } 8
{ var, sd }
{ varsum, length, var, mean, med, var, sd }
Edge
Use
(1, 2)
(2, 3)
(3, 4)
{ i, length }
(4, 3)
(3, 5)
(5, 6)
(6, 7)
(7, 6)
(6, 8)

22. DU Pairs for Stats defs come before uses, do not count as DU pairs
variable
DU Pairs
numbers
(1, 4) (1, 5) (1, 7)
length
(1, 5) (1, 8) (1, (3,4)) (1, (3,5)) (1, (6,7)) (1, (6,8))
med
(5, 8)
var
(8, 8) sd
mean
(5, 7) (5, 8)
sum
(1, 4) (1, 5) (4, 4) (4, 5)
varsum
(5, 7) (5, 8) (7, 7) (7, 8) i
(2, 4) (2, (3,4)) (2, (3,5)) (2, 7) (2, (6,7)) (2, (6,8))
(4, 4) (4, (3,4)) (4, (3,5)) (4, 7) (4, (6,7)) (4, (6,8))
(5, 7) (5, (6,7)) (5, (6,8))
(7, 7) (7, (6,7)) (7, (6,8))
defs after use in loop, these are valid DU pairs
No def-clear path …
different scope for i
No path through graph from nodes 5 and 7 to 4 or 3

23. DU Paths for Stats variable DU Pairs DU Paths numbers (1, 4) (1, 5)
(1, 7)
[ 1, 2, 3, 4 ]
[ 1, 2, 3, 5 ]
[ 1, 2, 3, 5, 6, 7 ]
length
(1, 8)
(1, (3,4))
(1, (3,5))
(1, (6,7))
(1, (6,8))
[ 1, 2, 3, 5, 6, 8 ]
med
(5, 8)
[ 5, 6, 8 ]
var
(8, 8)
No path needed sd
sum
(4, 4)
(4, 5)
[ 4, 3, 4 ]
[ 4, 3, 5 ]
variable
DU Pairs
DU Paths
mean
(5, 7)
(5, 8)
[ 5, 6, 7 ]
[ 5, 6, 8 ]
varsum
(7, 7)
(7, 8)
[ 7, 6, 7 ]
[ 7, 6, 8 ] i
(2, 4)
(2, (3,4))
(2, (3,5))
(4, 4)
(4, (3,4))
(4, (3,5))
(5, (6,7))
(5, (6,8))
(7, (6,7))
(7, (6,8))
[ 2, 3, 4 ]
[ 2, 3, 5 ]
[ 4, 3, 4 ]
[ 4, 3, 5 ]

24. DU Paths for Stats – No Duplicates
There are 38 DU paths for Stats, but only 12 unique
[ 1, 2, 3, 4 ]
[ 1, 2, 3, 5 ]
[ 1, 2, 3, 5, 6, 7 ]
[ 1, 2, 3, 5, 6, 8 ]
[ 2, 3, 4 ]
[ 2, 3, 5 ]
[ 4, 3, 4 ]
[ 4, 3, 5 ]
[ 5, 6, 7 ]
[ 5, 6, 8 ]
[ 7, 6, 7 ]
[ 7, 6, 8 ]
2 require at least two iterations of a loop
6 require at least one iteration of a loop
4 expect a loop not to be “entered”

25. Test Cases and Test Paths
Test Case : numbers = (44) ; length = 1
Test Path : [ 1, 2, 3, 4, 3, 5, 6, 7, 6, 8 ]
Additional DU Paths covered (no sidetrips)
[ 1, 2, 3, 4 ] [ 2, 3, 4 ] [ 4, 3, 5 ] [ 5, 6, 7 ] [ 7, 6, 8 ]
The five stars that require at least one iteration of a loop
Test Case : numbers = (2, 10, 15) ; length = 3
Test Path : [ 1, 2, 3, 4, 3, 4, 3, 4, 3, 5, 6, 7, 6, 7, 6, 7, 6, 8 ]
DU Paths covered (no sidetrips)
[ 4, 3, 4 ] [ 7, 6, 7 ]
The two stars that require at least two iterations of a loop
Other DU paths require arrays with length 0 to skip loops
But the method fails with index out of bounds exception…
med = numbers [length / 2];
A fault was
found

26. Example: Def-Use Associations
read (z) x = 0 y = 0 if (z  0) {
x = sqrt (z) if (0  x && x  5) y = f (x) else y = h (z) }
y = g (x, y)
print (y)
def-use associations for variable z.

27. Example: Def-Use Associations
read (z) x = 0 y = 0 if (z  0) {
x = sqrt (z) if (0  x && x  5)
y = f (x) else y = h (z) }
y = g (x, y)
print (y)
def-use associations for variable x.

28. Example: Def-Use Associations
read (z) x = 0 y = 0 if (z  0) {
x = sqrt (z) if (0  x && x  5) y = f (x) else y = h (z) }
y=g (x, y)
print (y)
def-use associations for variable y.

29. Using Control-flow Testing to Test Function ABS
Consider the following function:
/* ABS
This program function returns the absolute value of the integer
passed to the function as a parameter.
INPUT: An integer.
OUTPUT: The absolute value if the input integer. */
1                  int ABS(int x)
2                  {
3                  if (x < 0)
4                  x = -x;
5                  return x;
6                  }

30. Example: Using Control-flow Testing to Test Program COUNT
Consider the following program:
/* COUNT
This program counts the number of characters and lines in a text file.
INPUT: Text File
OUTPUT: Number of characters and number of lines. */
1                  main(int argc, char *argv[])
2                  {
3                  int numChars = 0;
4                  int numLines = 0;
5                  char chr;
6                  FILE *fp = NULL;
7                 

31. Program COUNT (Cont’d)
8                  if (argc < 2)
9                  {
10              printf(“\nUsage: %s <filename>”, argv[0]);
11              return (-1);
12              }
13              fp = fopen(argv[1], “r”);
14              if (fp == NULL)
15              {
16              perror(argv[1]); /* display error message */
17              return (-2);
18              }

32. Program COUNT (Cont’d)
while (!feof(fp))
20              {
21              chr = getc(fp); /* read character */
22              if (chr == ‘\n’) /* if carriage return */
23              numLines;
24              else
25              numChars;
26              }
27              printf(“\nNumber of characters = %d”, numChars);
28              printf(“\nNumber of lines = %d”, numLines);
29              }

33. An example: All-du-paths
What are all the du-paths in the following program ?
read (x,y);
for (i = 1; i <= 2; i++)
print (“hello”);
if (y < 0)
print (x);

34. Example: pow(x,y)

35. Def-Use Pairs (3) /** Euclid's algorithm */ public class GCD {
public int gcd(int x, int y) {
int tmp; // A: def x, y, tmp
while (y != 0) { // B: use y
tmp = x % y; // C: def tmp; use x, y
x = y; // D: def x; use y
y = tmp; // E: def y; use tmp }
return x; // F: use x
Data flow information is associated with locations in the program, or equivalently, with nodes in the program control flow graph. We mark each location with the sets of variables defined and used at those locations. Note that in node A (beginning of the procedure) x, y, and tmp are defined. x and y receive the values passed to them through parameters, while the declaration of tmp is treated like an assignment of a special value “uninitialized”.
Line c (node c in the graph at right) shows how an assignment statement typically defines one thing (tmp, in this case) and uses all the variables that are used in computing that value (x and y, in this case).
Line F (node f at right) shows that returning a value from a method or function is also a use of that value. Essentially we are considering that the return value will be used where the function or method is called.

36. Find all DU for x and y
Public int gcd (int x, int y) { int tmp; While (y!= 0) tmp= x % y; x = y; y = tmp; } return x;

37. Call Graph The most common graph for structural design testing
Nodes : Units (in Java – methods)
Edges : Calls to units
Example call graph A B C D F E
Node coverage : call every unit at least once (method coverage)
Edge coverage : execute every call at least once (call coverage)

38. Overestimating the calls relation
The static call graph includes calls through dynamic bindings that never occur in execution.
public class C {
public static C cFactory(String kind) {
if (kind == "C") return new C();
if (kind == "S") return new S();
return null; }
void foo() {
System.out.println("You called the parent's method");
public static void main(String args[]) {
(new A()).check();
class S extends C {
System.out.println("You called the child's method");
class A {
void check() {
C myC = C.cFactory("S");
myC.foo();
A.check()
C.foo()
S.foo()
CcFactory(string)

39. Contex Insensitive Call graphs
public class Context {
public static void main(String args[]) {
Context c = new Context();
c.foo(3);
c.bar(17); }
void foo(int n) {
int[] myArray = new int[ n ];
depends( myArray, 2) ;
void bar(int n) {
depends( myArray, 16) ;
void depends( int[] a, int n ) {
a[n] = 42;
main
C.foo
C.bar
C.depends

40. Contex Sensitive Call graphs
public class Context {
public static void main(String args[]) {
Context c = new Context();
c.foo(3);
c.bar(17); }
void foo(int n) {
int[] myArray = new int[ n ];
depends( myArray, 2) ;
void bar(int n) {
depends( myArray, 16) ;
void depends( int[] a, int n ) {
a[n] = 42;
main
C.foo(3)
C.bar(17)
C.depends(int(3),a,2)
C.depends (int(3),a,2)

41. Context Sensitive CFG exponential growthB D F H C E G I J
1 context A
2 contexts AB AC
4 contexts ABD ABE ACD ACE
8 contexts …
16 calling contexts …

42. Data Flow at the Design Level
Caller : A unit that invokes another unit
Callee : The unit that is called
Callsite : Statement or node where the call appears
Actual parameter : Variable in the caller
Formal parameter : Variable in the callee

43. Example Call Site A  B (x)  end A B (Y)  end B interface
Caller
interface
Actual Parameter
Callee
Formal Parameter
Applying data flow criteria to def-use pairs between units is too expensive
Too many possibilities
But this is integration testing, and we really only care about the interface …

44. Inter-procedural DU Pairs
If we focus on the interface, then we just need to consider the last definitions of variables before calls and returns and first uses inside units and after calls
Last-def : The set of nodes that define a variable x and has a def-clear path from the node through a callsite to a use in the other unit
Can be from caller to callee (parameter or shared variable) or from callee to caller as a return value
First-use : The set of nodes that have uses of a variable y and for which there is a def-clear and use-clear path from the callsite to the nodes

45. Example Inter-procedural DU Pairs
Caller
x = 5
x = 4
x = 3
B (x) 1 2 3 4 F
X = 14  y = G (x)  print (y)
callsite
first-use
last-def
DU pair 11
B (int y)
Z = y
T = y
print (y) 10 12 13
DU pair
Callee
G (a)
print (a)  b = 42  return (b)
Last Defs 2, 3
First Uses 11, 12

46. Example – Quadratic
ok = Root (X, Y, Z); if (ok) System.out.println (“Quadratic: ” + Root1 + Root2); else System.out.println (“No Solution.”); } // Three positive integers, finds quadratic root private static boolean Root (int A, int B, int C) { float D; boolean Result; D = (float) Math.pow ((double)B,
(double2-4.0)*A*C ); if (D < 0.0) { Result = false;
return (Result); } Root1 = (float) ((-B + Math.sqrt(D))/(2.0*A)); Root2 = (float) ((-B – Math.sqrt(D))/(2.0*A)); Result = true; return (Result); } / /End method Root } // End class Quadratic
1 // Program to compute the quadratic root for two numbers 2 import java.lang.Math; 3 4 class Quadratic 5 { 6 private static float Root1, Root2; 7 8 public static void main (String[] argv) 9 { int X, Y, Z; boolean ok; int controlFlag = Integer.parseInt (argv[0]); if (controlFlag == 1) { X = Integer.parseInt (argv[1]); Y = Integer.parseInt (argv[2]); Z = Integer.parseInt (argv[3]); } else {
X = 10; Y = 9; Z = 12; }
© Ammann & Offutt

47. shared variables last-defs
1 // Program to compute the quadratic root for two numbers 2 import java.lang.Math; 3 4 class Quadratic 5 { 6 private static float Root1, Root2; 7 8 public static void main (String[] argv) 9 { int X, Y, Z; boolean ok; int controlFlag = Integer.parseInt (argv[0]); if (controlFlag == 1) { X = Integer.parseInt (argv[1]); Y = Integer.parseInt (argv[2]); Z = Integer.parseInt (argv[3]); } else {
X = 10; Y = 9; Z = 12; }
shared variables
last-defs

48. first-use first-use last-def last-defs
ok = Root (X, Y, Z); if (ok) System.out.println (“Quadratic: ” + Root1 + Root2); else System.out.println (“No Solution.”); } // Three positive integers, finds the quadratic root private static boolean Root (int A, int B, int C) { float D; boolean Result; D = (float) Math.pow ((double)B, (double2-4.0)*A*C); if (D < 0.0) { Result = false;
return (Result); } Root1 = (float) ((-B + Math.sqrt(D)) / (2.0*A)); Root2 = (float) ((-B – Math.sqrt(D)) / (2.0*A)); Result = true; return (Result); } / /End method Root } // End class Quadratic
first-use
first-use
last-def
last-defs

49. Quadratic – Coupling DU-pairs
Pairs of locations: method name, variable name, statement
(main (), X, 15) – (Root (), A, 38)
(main (), Y, 16) – (Root (), B, 38)
(main (), Z, 17) – (Root (), C, 38)
(main (), X, 21) – (Root (), A, 38)
(main (), Y, 22) – (Root (), B, 38)
(main (), Z, 23) – (Root (), C, 38)
(Root (), Root1, 44) – (main (), Root1, 28)
(Root (), Root2, 45) – (main (), Root2, 28)
(Root (), Result, 41) – ( main (), ok, 26 )
(Root (), Result, 46) – ( main (), ok, 26 )

50. Types of Def-Use Pairs def use A () intra-procedural data flow
(within the same unit)
inter-procedural data flow
def A ()
B () use
last-def A ()
first-use B ()
full
coupling
def A()
use B()
A()
B()
F ()
object-oriented direct coupling data flow
object-oriented indirect coupling data flow
def A()
use B()
M ()
N()
F()
A() M()
B() N()

51. Example of Control Flow Graph
public static String collapseNewlines(String argStr) {
char last = argStr.charAt(0);
StringBuffer argBuf = new StringBuffer();
for (int cIdx = 0 ; cIdx < argStr.length(); cIdx++)
char ch = argStr.charAt(cIdx);
if (ch != '\n' || last != '\n')
argBuf.append(ch);
last = ch; }
return argBuf.toString();

52. File ADT Example class FileADT has three methods:
open (String fName) // Opens file with name fName
close () // Closes the file and makes it unavailable
write (String textLine) // Writes a line of text to the file s1 s2 s3 s4 s5 s6
open (f)
write(t)
write (t)
close ()
Valid sequencing constraints on FileADT:
An open (f) must be executed before every write (t)
An open (f) must be executed before every close ()
A write (f) may not be executed after a close () unless there is an open (f) in between
A write (t) should be executed before every close ()

53. Is there a path that violates any of the sequencing constraints ?
Static Checking
Is there a path that violates any of the sequencing constraints ? s1 s2 s3 s4 s5 s6
open (f)
write(t)
write (t)
close ()
Is there a path to a write() that does not go through an open() ?
Is there a path to a close() that does not go through an open() ?
Is there a path from a close() to a write()?
Is there a path from an open() to a close() that does not go through a write() ? (“write-clear” path)
[ 1, 3, 4, 6 ] – ADT use anomaly!

54. Static Checking Consider the following graph :
close () s1 s2 s3 s4 s5 s8
open (f)
write (t) s6 s7
[ 7, 3, 4 ] – close () before write () !

55. Inheritance & Polymorphism
Caution : Ideas are preliminary and not widely used
Example inheritance hierarchy graph A B C D
Classes are not executable, so this graph is not directly testable
We need objects A B C D a b d c
objects
What is coverage on this graph ?

56. Coverage on Inheritance Graph
Create an object for each class ?
This seems weak because there is no execution
Create an object for each class and apply call coverage?
OO Call Coverage : TR contains each reachable node in the call graph of an object instantiated for each class in the class hierarchy.
OO Object Call Coverage : TR contains each reachable node in the call graph of every object instantiated for each class in the class hierarchy.
Data flow is probably more appropriate …

57. Access Control (in Java)
Class 1
Package
public members
protected members
Class 3
default
private members
inheritance
Class 2
Class 5
Class 4
© Ammann and Offutt

58. Additional Definitions
Inheritance : If class B inherits from class A, then all variables and methods in A are implicitly in B, and B can add more
A is the parent or ancestor
B is the child or descendent
An object reference obj that is declared to be of type A can be assigned an object of either type A, B, or any of B’s descendents
Declared type : The type used in the declaration: A obj;
Actual type : The type used in the object assignment: obj = new B();
Class (State) Variables : The variables declared at the class level, often private

59. Polymorphism
The same variable can have different types depending on the program execution
If B inherits from A, then an object of type B can be used when an object of type A is expected
If both A and B define the same method M (B overrides A), then the same statement might call either A’s version of M or B’s version

60. Testing OO Software
Intra-method testing : Testing individual methods within classes
Inter-method testing : Multiple methods within a class are tested in concert
Intra-class testing : Testing a single class, usually using sequences of calls to methods within the class
Inter-class testing : More than one class is tested at the same time (integration)

61. Example DU Pairs and Anomalies
Consider what happens when an overriding method has a different def-set than the overridden method B
+h ()
+i () -x A -u -v -w
+h()
+i()
+j()
+l() C
+j () -y
def-use
Method
Defs
Uses
A::h ()
{A::u, A::w}
A::i ()
{A::u}
A::j ()
{A::v}
{A::w}
A::l()
B::h()
{B::x}
B::i()
C::i()
C::j()
{C::y}
A::h() calls j(), B::h() does not DU
anomaly DU
anomaly
def-use

62. Polymorphism Headaches (Yo-Yo)
Actual
type A
d()
g()
h()
i()
j()
l()
+d ()
+g ()
+h ()
+i ()
+j ()
+l () B
h()
i()
k() C
i()
j()
l()
Object is of actual type A
A::d ()

63. Polymorphism Headaches (Yo-Yo)
g()
h()
i()
j()
l()
+d ()
+g ()
+h ()
+i ()
+j ()
+l () B
h()
i()
k() C
i()
j()
l() A
d()
g()
h()
i()
j()
l() B
Actual
type
+h ()
+i ()
+k () B
h()
i()
k() C
i()
j()
l()
Object is of actual type B
B::d ()

64. Polymorphism Headaches (Yo-Yo)
g()
h()
i()
j()
l()
+d ()
+g ()
+h ()
+i ()
+j ()
+l () B
h()
i()
k() C
i()
j()
l() A
d()
g()
h()
i()
j()
l() B
+h ()
+i ()
+k () B
h()
i()
k() C
i()
j()
l() A
d()
g()
h()
i()
j()
l() B
h()
i()
k() C
Actual
type
+i ()
+j ()
+l () C
i()
j()
l()
Object is of actual type C, C::d ()

65. OO Faults and Anomalies
Acronym
Fault / Anomaly
ITU
Inconsistent Type Use
SDA
State Definition Anomaly
SDIH
State Definition Inconsistency
SDI
State Defined Incorrectly
IISD
Indirect Inconsistent State Definition
ACB1
Anomalous Construction Behavior (1)
ACB2
Anomalous Construction Behavior (2) IC
Incomplete Construction
SVA
State Visibility Anomaly

66. Inconsistent Type Use (ITU)
No overriding (no polymorphism)
C extends T, and C adds new methods (extension)
An object is used “as a C”, then as a T, then as a C
Methods in T can put object in state that is inconsistent for C
s.push (“Steffi”);
s.push (“Joyce”);
s.push (“Andrew”);
dumb (s);
s.pop();
void dumb (Vector v) {
v.removeElementAt (v.size()-1); }
Vector
-array
+insertElementAt()
+removeElementAt()
// Stack is empty!
Stack
+pop (): Object
+push (): Object
call
call

67. State Definition Anomaly (SDA)
X extends W, and X overrides some methods
The overriding methods in X fail to define some variables that the overridden methods in W defined W v u
m()
n() X x Y w
W::m () defines v and W::n() uses v
X::n () uses v
Y::m () does not define v
For an object of actual type Y, a data flow anomaly exists and results in a fault if m() is called, then n()

68. State Definition Inconsistency (SDIH)
Hiding a variable, possibly accidentally
If the descendant’s version of the variable is defined, the ancestor’s version may not be W v u
m()
n() X x Y
Y overrides W’s version of v
Y::m() defines Y::v
X::n() uses v … getting W’s version of v
For an object of type Y, a data flow inconsistency may exist and result in a fault if m() is called, then n()
overrides
(hides)

69. Anomalous Construction Behavior (ACB1)
Constructor of W calls a method f()
A child of W, X, overrides f()
X::f() uses variables that should be defined by X’s constructor W
W()
f() X x
Calls
Uses
Overrides
When an object of type X is constructed, W() is run before X().
When W() calls X::f(), x is used, but has not yet been given a value!

70. State Visibility Anomaly (SVA)
A private variable v is declared in ancestor W, and v is defined by W::m()
X extends W and Y extends X
Y overrides m(), and calls W::m() to define v W -v
m() X Y
Overrides,
calls W -v
m() X Y
Overrides,
calls
Overrides
X::m() is added later
Y:m() can no longer call W::m()!

71. Need to consider the set of interactions that can occur:
Testing Goals
We want to test how a method can interact with instance bound to object o:
Interactions occur through the coupling sequences
Need to consider the set of interactions that can occur:
What types can be bound to o?
Which methods can actually execute? (polymorphic call sets)
Test all couplings with all type bindings possible

72. Web Applications and Other Distributed Software
use B() P1
def A()
message P2
distributed software data flow
“message” could be HTTP, RMI, or other mechanism
A() and B() could be in the same class or accessing a persistent variable such as in a web session
Beyond current technologies