1. ECE 453 – CS 447 – SE 465 Software Testing & Quality Assurance Instructor Kostas Kontogiannis

2. These slides are based on:
Lecture slides by Ian Summerville, see
ECE355 Lecture slides by Sagar Naik
Lecture Notes from Bernd Bruegge, Allen H. Dutoit “Object-Oriented Software Engineering – Using UML, Patterns and Java”

3. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

4. Static and dynamic V&V Static verification Requirements specification
Architecture
Detailed
design
Implementation V1
Implementation V2
Prototype
Dynamic
V &V
Special cases
Executable specifications
Animation of formal specs

5. Program testing Can reveal the presence of errors NOT their absence
Only exhaustive testing can show a program is free from defects. However, exhaustive testing for any but trivial programs is impossible
A successful test is a test which discovers one or more errors
Should be used in conjunction with static verification
Run all tests after modifying a system
©Ian Sommerville 1995

6. Testing in the V-Model Acceptance Requirements test Customer Developer
Architectural
Design
System test
Run tests
Integration test
Write tests
Detailed
Design
Functional
(BB)
Structural
(WB)
Module
implementation
Unit test

7. Testing stages Unit testing Integration testing System testing
Testing of individual components
Integration testing
Testing to expose problems arising from the combination of components
System testing
Testing the complete system prior to delivery
Acceptance testing
Testing by users to check that the system satisfies requirements. Sometimes called alpha testing

8. Types of testing Statistical testing Defect testing
Tests designed to reflect the frequency of user inputs. Used for reliability estimation.
Covered in section on Software reliability.
Defect testing
Tests designed to discover system defects.
A successful defect test is one which reveals the presence of defects in a system.
©Ian Sommerville 1995

9. Some Terminology Failure Error Fault
A failure is said to occur whenever the external behavior does not conform to system spec.
Error
An error is a state of the system which, in the absence of any corrective action, could lead to a failure.
Fault
An adjudged cause of an error.

10. Some Terminology fault, bug, error, defect It is there in the program…
Program state
Error
Observed
Failure

11. Testing Activities Unit T est Unit T est Integration Functional Test
Requirements
Analysis
Document
Subsystem
Code
Unit
Requirements
Analysis
Document
System
Design
Document T
est
Tested
Subsystem
User
Manual
Subsystem
Code
Unit T
est
Tested
Subsystem
Integration
Functional
Test
Test
Functioning
System
Integrated
Subsystems
Tested Subsystem
Subsystem
Code
Unit T
est
All tests by developer

12. Testing Activities continued
Client’s
Understanding
of Requirements
Global
Requirements
User
Environment
Validated
System
Accepted
System
Functioning
System
Performance
Acceptance
Installation
Test
Test
Test
Usable
System
Tests by client
Tests by developer
User’s understanding
System in
Use
Tests (?) by user

13. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

14. Testing and debugging
Defect testing and debugging are distinct processes
Defect testing is concerned with confirming the presence of errors
Debugging is concerned with locating and repairing these errors
Debugging involves formulating a hypothesis about program behaviour then testing these hypotheses to find the system error
©Ian Sommerville 1995

15. Debugging Activities Locate error & fault Design fault repair
Repair fault
Re-test
program
©Ian Sommerville 1995

16. Testing Activities Test result Identify
Test conditions (“What”): an item or event to be verified.
How the “what” can be tested: realization
Design
Build test cases (imp. scripts, data)
Build
Run the system
Execute
Test case outcome with
expected outcome
Compare
Test result

17. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

18. Goodness of test cases Exec. of a test case against a program P
Covers certain requirements of P;
Covers certain parts of P’s functionality;
Covers certain parts of P’s internal logic.
 Idea of coverage guides test case selection.

19. Black-box Testing
Focus: I/O behavior. If for any given input, we can predict the output, then the module passes the test.
Almost always impossible to generate all possible inputs ("test cases")
Goal: Reduce number of test cases by equivalence partitioning:
Divide input conditions into equivalence classes
Choose test cases for each equivalence class. (Example: If an object is supposed to accept a negative number, testing one negative number is enough)

20. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

21. White-box Testing
Statement Testing (Algebraic Testing): Test single statements (Choice of operators in polynomials, etc)
Loop Testing:
Cause execution of the loop to be skipped completely. (Exception: Repeat loops)
Loop to be executed exactly once
Loop to be executed more than once
Path testing:
Make sure all paths in the program are executed
Branch Testing (Conditional Testing): Make sure that each possible outcome from a condition is tested at least once
if ( i =
TRUE) printf("YES\n");
else
printf("NO\n");
Test cases: 1) i = TRUE; 2) i = FALSE

22. Code Coverage Statement coverage
Elementary statements: assignment, I/O, call
Select a test set T such that by executing P in all cases in T, each statement of P is executed at least once.
read(x); read(y);
if x > 0 then write(“1”);
else write(“2”);
if y > 0 then write(“3”);
else write(“4”);
T: {<x = -13, y = 51>, <x = 2, y = -3>}

23. White-box Testing: Determining the Paths
FindMean (FILE ScoreFile)
{ float SumOfScores = 0.0;
int NumberOfScores = 0;
float Mean=0.0; float Score;
Read(ScoreFile, Score);
while (! EOF(ScoreFile) {
if (Score > 0.0 ) {
SumOfScores = SumOfScores + Score;
NumberOfScores++; }
/* Compute the mean and print the result */
if (NumberOfScores > 0) {
Mean = SumOfScores / NumberOfScores;
printf(“ The mean score is %f\n”, Mean);
} else
printf (“No scores found in file\n”); 1 2 3 4 5 6 7 8 9

24. Constructing the Logic Flow Diagram

25. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

26. Unit Testing
Objective: Find differences between specified units and their imps.
Unit: component ( module, function, class, objects, …)
Unit test environment:
Driver
Test cases
Test result
Effectiveness?
Partitioning
Code coverage
Unit under
test
Stub
Stub
Dummy modules

27. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

28. Integration Testing Objectives: Problem areas
To expose problems arising from the combination
To quickly obtain a working solution from components.
Problem areas
Internal: between components
Invocation: call/message passing/…
Parameters: type, number, order, value
Invocation return: identity (who?), type, sequence
External:
Interrupts (wrong handler?)
I/O timing
Interaction

29. Integration Testing Types of integration Structural Behavioral
“Big bang”  no error localization
Bottom-up: terminal, driver/module, (driver  module)
Top-down: top, stubs, (stub  module), early demo
Behavioral
(next slide)

30. Integration Testing (Behavioral: Path-Based)C
MM-path: Interleaved sequence of module exec path and messages
Module exec path: entry-exit path in the same module
Atomic System Function: port input, … {MM-paths}, … port output
Test cases: exercise ASFs

31. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

32. System Testing Concerns with the app’s externals
Much more than functional
Load/stress testing
Usability testing
Performance testing
Resource testing

33. System Testing Functional testing
Objective: Assess whether the app does what it is supposed to do
Basis: Behavioral/functional specification
Test case: A sequence of ASFs (thread)

34. System Testing Functional testing: coverage Event-based coverage
PI1: each port input event occurs
PI2: common sequences of port input event occurs
PI3: each port input in every relevant data context
PI4: for a given context, all possible input events
PO1: each port output event
PO2: each port output event occurs for each cause
Data-based
DM1: Exercise cardinality of every relationship
DM2: Exercise (functional) dependencies among relationships

35. System Testing Stress testing: push it to its limit + beyond Volume
Application
(System)
Users
response :
rate
Resources: phy. + logical

36. System Testing Performance testing Usability testing
Performance seen by
users: delay, throughput
System owner: memory, CPU, comm
Performance
Explicitly specified or expected to do well
Unspecified  find the limit
Usability testing
Human element in system operation
GUI, messages, reports, …

37. Test Stopping Criteria
Meet deadline, exhaust budget, …  management
Achieved desired coverage
Achieved desired level failure intensity

38. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

39. Acceptance Testing Purpose: ensure that end users are satisfied
Basis: user expectations (documented or not)
Environment: real
Performed: for and by end users (commissioned projects)
Test cases:
May reuse from system test
Designed by end users

40. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations

41. Regression Testing
Whenever a system is modified (fixing a bug, adding functionality, etc.), the entire test suite needs to be rerun
Make sure that features that already worked are not affected by the change
Automatic re-testing before checking in changes into a code repository
Incremental testing strategies for big systems

42. Comparison of White & Black-box Testing 25.1.2002
White-box Testing:
Potentially infinite number of paths have to be tested
White-box testing often tests what is done, instead of what should be done
Cannot detect missing use cases
Black-box Testing:
Potential combinatorical explosion of test cases (valid & invalid data)
Often not clear whether the selected test cases uncover a particular error
Does not discover extraneous use cases ("features")
Both types of testing are needed
White-box testing and black box testing are the extreme ends of a testing continuum.
Any choice of test case lies in between and depends on the following:
Number of possible logical paths
Nature of input data
Amount of computation
Complexity of algorithms and data structures

43. The 4 Testing Steps 1. Select what has to be measured
Analysis: Completeness of requirements
Design: tested for cohesion
Implementation: Code tests
2. Decide how the testing is done
Code inspection
Proofs (Design by Contract)
Black-box, white box,
Select integration testing strategy (big bang, bottom up, top down, sandwich)
3. Develop test cases
A test case is a set of test data or situations that will be used to exercise the unit (code, module, system) being tested or about the attribute being measured
4. Create the test oracle
An oracle contains of the predicted results for a set of test cases
The test oracle has to be written down before the actual testing takes place

44. Guidance for Test Case Selection
Use analysis knowledge about functional requirements (black-box testing):
Use cases
Expected input data
Invalid input data
Use design knowledge about system structure, algorithms, data structures (white-box testing):
Control structures
Test branches, loops, ...
Data structures
Test records fields, arrays, ...
Use implementation knowledge about algorithms:
Examples:
Force division by zero
Use sequence of test cases for interrupt handler

45. Unit-testing Heuristics
1. Create unit tests as soon as object design is completed:
Black-box test: Test the use cases & functional model
White-box test: Test the dynamic model
Data-structure test: Test the object model
2. Develop the test cases
Goal: Find the minimal number of test cases to cover as many paths as possible
3. Cross-check the test cases to eliminate duplicates
Don't waste your time!
4. Desk check your source code
Reduces testing time
5. Create a test harness
Test drivers and test stubs are needed for integration testing
6. Describe the test oracle
Often the result of the first successfully executed test
7. Execute the test cases
Don’t forget regression testing
Re-execute test cases every time a change is made.
8. Compare the results of the test with the test oracle
Automate as much as possible

46. Overview Basics of Testing Testing & Debugging Activities
Testing Strategies
Black-Box Testing
White-Box Testing
Testing in the Development Process
Unit Test
Integration Test
System Test
Acceptance Test
Regression Test
Practical Considerations