1. Presentation of a paper on “Model-based Software Testing”
Dr. Kasi Periyasamy
Department of Computer Science

2. Reference
F. Bouquet et al., “A Subset of Precise UML for Model-Based Testing”, Workshop on Advances in Model-Based Software Testing (A-MOST 07), Part of International Symposium on Software Testing and Analysis (ISSTA 2007), London, UK, July 2007, pp. 95 – 104.

3. About the authors F. Bouquet, University of Besançon, France.
C. Grandpierre, B. Legeard, F. Peureux and N. Vacelet, LEIRIOS, France.
M. Utting, University of Waikato, New Zealand.

4. Objective and Approach
Demonstrate the use of UML for Model-Based Testing
Approach
Define an executable subset of UML and use it for Model-Based Testing
The work uses UML class diagram, state diagram and OCL (Object Constraint Language) for defining the model
A tool has been developed to automate the testing process

5. Definition of Model-Based Testing
Definition given by the authors
A process to automatically generate test cases and executable test scripts from a behavioral model of the system under test (SUT)
The model formalizes the expected behavior so that it is easy for analysis and automation

6. Notations and Tools A subset of UML 2.1 is chosen, named as UML-MBT
Class Diagram, Object Diagram, State Diagram, and Object Constraint Language (OCL)
Slightly different from UML 2.1; changes are made to support practical model-based testing
In particular, OCL 2.0 is modified (explained in later slides)
LEIRIOS Test Designer tool was used to automatically generate the test cases
Uses theorem proving technology

7. Restrictions
Only Integer, Boolean, Enumerated type and Object type are supported
Specific range of integers are chosen because of implementation constraints
Inheritance and Association classes in Class Diagram are not considered
Dynamic creation and deletion of objects are not considered
All objects are shown in the object diagram at the very beginning of the testing process
Semantics of State machine processing assumes “Run-to-Completion” of transitions

8. Passive and Active OCL expressions
The expression is treated as a condition and yields a Boolean result
E.g., variable = true
Pre-conditions and other constraints
Active
The expression is evaluated and a value is assigned to the variable on L.H.S.
E.g., variable = true
Post-conditions and actions

9. Operators in OCL
Boolean operators: ‘=’, ‘<>’, ‘or’, ‘and’, ‘not’, ‘xor’
Arithmetic operators: All standard operators
Operators on Enumerated types: ‘=’ , ‘<>’
Operators on classes and objects: ‘=’, ‘<>’,
obj.oclIsUndefined() ……. Boolean
class.allInstances() … Set

10. Operators in OCL (continued)
Operators on collections: ‘=’, ‘<>’,
coll->size(), coll->includes(obj), coll->excludes(obj),
coll->includesAll (set), coll->excludedAll (set),
coll->isEmpty(), coll->notEmpty(),
coll->including (obj), coll->excluding (obj)
The last two operators return sets while others (except size()) return Boolean results.

11. Operators in OCL (continued)
Iterative operators on collections:
coll->collect (obj), coll->select (bool exp)
The above operations return sets
coll->exists (bool exp), coll->forAll (bool exp)
The above two operations return Boolean results
coll->any (bool exp)
The above operation returns an object

12. Behavioral Description
Context: Triangle::getType (a:Integer, b:Integer, c:Integer) : TYPE
Pre: a > 0 and b > 0 and c > 0
Post:
If (a+b <= c or b+c <= a or c+a <= b) then
Result = TYPE::NOT_A_TRIANGLE
Else
If (a = b or b = c or c = a) then
If (a = b and b = c) then
Result = TYPE::EQUILATERAL
Else Result = TYPE::ISOCELES
Endif
Result = TYPE::SCALANE

13. Undefined value Different from OCL semantics from UML 2.1
Coll->any (bool exp) may return an undefined value when no object in the collection satisfies the boolean expression
Expr.role may return an undefined value when the expression evaluates to a non-existing object or the role identifies a non-existing object
Remember that all objects must be available in the object diagram before the testing process is started
Divide by zero execution results in undefined value

14. Application Example - Stack
0..1
Points to
Max : Integer
Size : Integer
+stack
+up
+top
0..1
0..1
Pop ()
Push ()
Element
isOn
+stack 1
0..*
0..1
+elements
takesFrom
+down 1
+pool
0..1
Pool
emptyOut ()
fillOut ()
+pool
contains
© F.Bouquet, A-MOST 2007

15. Object diagram stack: Stack pool: Pool Max = 3 Size = 0 e2 : Element
© F. Bouquet, A-MOST 2007

16. State Diagram Pop() EmptyStackException Empty Push() Pop()[size=1]
Push()[size < max-1]
Pop()[size>1]
Loaded
Pop()
Push()[size = max-1]
Full
FullStackException
Push()
© F. Bouquest, A-MOST 2007

17. Results of test automation
Show tables from the paper

18. Conclusion by authors
Model-based testing demonstrated using a subset of UML 2.1
Testing process automated using LEIRIOS Test Design tool
Results are convincing
A lot of limitations to work around
Continuing work on more real-world problems

19. My comments Very interesting paper on model-based testing
Most attractive feature is the automation of test case generation using the state machine model and OCL behavioral description
I agree with the authors that the approach should be demonstrated for more real-world problems
Using UML reduces the learning curve on developing a model  a problem with other model-based techniques
The paper focuses more on the model and very little about actual testing process itself.