1. Chapter-5 (Testing Strategy)
Chapter-17(Pressman)

2. Software Testing Strategy
A Software Testing Strategy

3. Software Testing Steps
High-order tests
Integration test
Unit test
Testing
direction
code
design
requirements

4. Levels of Testing for Conventional Software
i) Unit testing
Concentrates on each component/function of the software as implemented in the source code
ii) Integration testing
Focuses on the design and construction of the software architecture
iii) Validation testing
Requirements are validated against the constructed software
iv) System testing
The software and other system elements are tested as a whole

5. Strategic Testing Issues
Specify product requirements in a quantifiable manner before testing starts.
Specify testing objectives explicitly.
Identify the user classes of the software and develop a profile for each.
Develop a test plan that emphasizes rapid cycle testing.
Build robust software that is designed to test itself Use effective formal reviews as a filter prior to testing.
Conduct formal technical reviews to assess the test strategy and test cases.

6. A Software Testing Strategy
System
Engineering
Requirements
Design
Code
Unit
Test
Integration
Validation

7. Logical Organization of Testing
( Not necessarily how it’s actually done! )
Component code
Unit test
Tested component
Component code
Unit test
Integration test
System test
Integrated modules
System in use
Ensures that all components work together
Component code
Unit test
Function test
Quality test
Acceptance test
Installation test
Ensure that each component works as specified
Verifies that functional requirements are satisfied
Verifies non-functional requirements
Customer verifies all requirements
Testing in user environment 7 7

8. COMPONENT/UNIT TESTING8

9. Unit Testing
Verification of the smallest unit in software - the module
White box oriented
Can be conducted in parallel for multiple modules
Unit test cases designed based on source code –
Test environment includes driver and/or stubs

10. Unit Test Environment interface local data structures
driver
interface
local data structures
Module
boundary conditions
independent paths
error handling paths
stub
stub
test cases
RESULTS

11. Drivers and Stubs for Unit Testing
A simple main program that accepts test case data, passes such data to the component being tested, and prints the returned results
Stubs
Serve to replace modules that are subordinate to (called by) the component to be tested
It uses the module’s exact interface, may do minimal data manipulation, provides verification of entry, and returns control to the module undergoing testing
Drivers and stubs both represent overhead
Both must be written but don’t constitute part of the installed software product

12. Driver
Module to
be tested
Stub
…..

13. Stubs and drivers Driver: Stub: A component, that calls the TestedUnit
Controls the test cases
Stub:
A component, the TestedUnit depends on
Partial implementation
Returns fake values.
Driver
Tested
Unit
Stub

14. 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

15. INTEGRATION TESTING 15

16. Logical Organization of Testing
( Not necessarily how it’s actually done! )
Component code
Unit test
Tested component
Component code
Unit test
Integration test
System test
Integrated modules
System in use
Ensures that all components work together
Component code
Unit test
Function test
Quality test
Acceptance test
Installation test
Ensure that each component works as specified
Verifies that functional requirements are satisfied
Verifies non-functional requirements
Customer verifies all requirements
Testing in user environment 16 16

17. Integration Testing
The entire system is viewed as a collection of subsystems (sets of classes) determined during the system and object design
Goal: Test all interfaces between subsystems and the interaction of subsystems
The Integration testing strategy determines the order in which the subsystems are selected for testing and integration.
For the selection of the subsystems we use the system decomposition from System Design
Kürzen?
Tonspur: Übergang Unit Test zu Integration

18. Why do we do integration testing?
Unit tests only test the unit in isolation
Many failures result from faults in the interaction of subsystems
Often many Off-the-shelf components are used that cannot be unit tested
Without integration testing the system test will be very time consuming
Failures that are not discovered in integration testing will be discovered after the system is deployed and can be very expensive.

19. Integration testing
Big bang
Bottom up
Top down
Sandwich
Continuous

20. Big-Bang Approach Test A Test B Test C Test A, B, C, D, Test D E, F, G
This unit tests each of the subsystems, and then does one gigantic integration test, in which all the subsystems are immediately tested together.
Don‘t try this!! Why: The interfaces of each of the subsystems have not been tested yet.
Test E
Test F
Test G

21. Bottom-up Testing Strategy
The subsystems in the lowest layer of the call hierarchy are tested individually
Then the next subsystems are tested that call the previously tested subsystems
This is repeated until all subsystems are included
Drivers are needed.

22. Bottom-up IntegrationC E F G D B A B C D
Test E E F G
Test B, E, F
Test F
This unit tests each of the subsystems, and then does one gigantic integration test, in which all the subsystems are immediately tested together.
Don‘t try this!! Why: The interfaces of each of the subsystems have not been tested yet.
Test
A, B, C, D,
E, F, G
Test C
Test G
Test D,G

23. Bottom Up Approach

24. Pros and Cons of Bottom-Up Integration Testing
Tests the most important subsystem (user interface) last
Drivers needed
Pro
No stubs needed
Useful for integration testing of the following systems
Object-oriented systems
Real-time systems
Systems with strict performance requirements.

25. Top-down Testing Strategy
Test the top layer or the controlling subsystem first
Then combine all the subsystems that are called by the tested subsystems and test the resulting collection of subsystems
Do this until all subsystems are incorporated into the test
Stubs are needed to do the testing.

26. Top-down Integration Test A, B, C, D, E, F, G Test A Test A, B, C, D
This unit tests each of the subsystems, and then does one gigantic integration test, in which all the subsystems are immediately tested together.
Don‘t try this!! Why: The interfaces of each of the subsystems have not been tested yet.
Test A
Test A, B, C, D
Layer I
Layer I + II
All Layers

27. Integration Testing for Structural Software
Top Down Integration A
top module is tested with
stubs B F G
stubs are replaced one at
a time, "depth first" C
as new modules are integrated,
some subset of tests is re-run D E

28. Pros and Cons of Top-down Integration Testing
Test cases can be defined in terms of the functionality of the system (functional requirements)
No drivers needed
Cons
Writing stubs is difficult: Stubs must allow all possible conditions to be tested.
Large number of stubs may be required, especially if the lowest level of the system contains many methods.
Some interfaces are not tested separately.

29. Sandwich Testing Strategy
Combines top-down strategy with bottom-up strategy
The system is viewed as having three layers
A target layer in the middle
A layer above the target
A layer below the target
Testing converges at the target layer.
How do you select the target layer if there are more than 3 layers?
Heuristic: Try to minimize the number of stubs and drivers

30. Sandwich Testing StrategyB C D
Test A E F G
Test A,B,C, D
Test E
Test
A, B, C, D,
E, F, G
Anpassen
Test B, E, F
Test F
Test D,G
Test G

31. Pros and Cons of Sandwich Testing
Top and Bottom Layer Tests can be done in parallel
Problem: Does not test the individual subsystems and their interfaces thoroughly before integration
Solution: Modified sandwich testing strategy

32. Modified Sandwich Testing Strategy
Test in parallel:
Middle layer with drivers and stubs
Top layer with stubs
Bottom layer with drivers
Top layer accessing middle layer (top layer replaces drivers)
Bottom accessed by middle layer (bottom layer replaces stubs).

33. Modified Sandwich TestingB C D
Test A
Test A,C
Test C E F G
Test B
Test
A, B, C, D,
E, F, G
Test E
Test B, E, F
Test F
Test D
Test D,G
Test G

34. Continuous/smoke Testing
Continuous build:
Build from day one
Test from day one
Integrate from day one
System is always run able
Requires integrated tool support:
Continuous build server
Automated tests with high coverage
Tool supported refactoring
Software configuration management
Issue tracking.

35. Smoke Testing
Software components already translated into code are integrated into a build.
A series of tests designed to expose errors that will keep the build from performing its functions are created.
The build is integrated with the other builds and the entire product is smoke tested daily using either top-down or bottom integration.

36. Continuous Testing Strategy
Spread SheetView
Layer I B C D
Data Model
Calculator
Currency
Converter
Layer II
SCRUM
Scheibe vom Brot XXXX E F G
BinaryFile Storage
XMLFile Storage
Currency DataBase
Layer III
+ Cells
+ Addition
Sheet View
+ File Storage

37. Steps in Integration Testing
1. Based on the integration strategy, select a component to be tested. Unit test all the classes in the component.
2. Put selected component together; do any preliminary fix-up necessary to make the integration test operational (drivers, stubs)
3. Test functional requirements: Define test cases that exercise all uses cases with the selected component
4. Test subsystem decomposition: Define test cases that exercise all dependencies
5. Test non-functional requirements: Execute performance tests
6. Keep records of the test cases and testing activities.
7. Repeat steps 1 to 7 until the full system is tested.
The primary goal of integration testing is to identify failures with the (current) component configuration. .

38. Validation Testing
A series of black box tests that demonstrate conformity with requirements
Test that software functions as expected by customer
Test plan and details can be based on software requirements specification

39. Logical Organization of Testing
( Not necessarily how it’s actually done! )
Component code
Unit test
Tested component
Component code
Unit test
Integration test
System test
Integrated modules
System in use
Ensures that all components work together
Component code
Unit test
Function test
Quality test
Acceptance test
Installation test
Ensure that each component works as specified
Verifies that functional requirements are satisfied
Verifies non-functional requirements
Customer verifies all requirements
Testing in user environment 39 39

40. System Testing
A series of tests to fully exercise a computer-based system
Verify that all system elements have been properly integrated and perform allocated functions
Software is one element to be integrated
Software engineer to anticipate potential interfacing problems

41. System Testing Functional Testing Performance Testing
Validates functional requirements
Performance Testing
Validates non-functional requirements
Acceptance Testing
Validates clients expectations
When we are system testing, we are testing all subsystems together.
The requirements have a large impact on the quality of system testing:
The more explicit the requirements, the easier they are to test.
We distinguish the following types of system testing
Let’s walk through each of these system testing types

42. Functional Testing Goal: Test functionality of system
Test cases are designed from the requirements analysis document (better: user manual) and centered around requirements and key functions (use cases)
The system is treated as black box
Unit test cases can be reused, but new test cases have to be developed as well.
Essentially the same as black box testing
Unit test cases can be reused, but in end user oriented systems new test cases have to be developed as well. .

43. Performance Testing Goal: Try to violate non-functional requirements
Test how the system behaves when overloaded.
Can bottlenecks be identified? (First candidates for redesign in the next iteration)
Try unusual orders of execution
Call a receive() before send()
Check the system’s response to large volumes of data
If the system is supposed to handle 1000 items, try it with 1001 items.
What is the amount of time spent in different use cases?
Are typical cases executed in a timely fashion?
Push the (integrated) system to its limits.

44. Types of Performance Testing
Stress/load Testing
Stress limits of system
Volume testing
Test what happens if large amounts of data are handled
Configuration testing
Test the various software and hardware configurations
Compatibility test
Test backward compatibility with existing systems
Timing testing
Evaluate response times and time to perform a function
Security testing
Try to violate security requirements
Environmental test
Test tolerances for heat, humidity, motion
Quality testing
Test reliability, maintain- ability & availability
Recovery testing
Test system’s response to presence of errors or loss of data
Human factors testing
Test with end users.
Stress Testing
Stress limits of system (maximum # of users, peak demands, extended operation)
Volume testing
Test what happens if large amounts of data are handled
Configuration testing
Test the various software and hardware configurations
Compatibility test
Test backward compatibility with existing systems
Security testing
Try to violate security requirements

45. Acceptance Testing
Goal: Demonstrate system is ready for operational use
Choice of tests is made by client
Many tests can be taken from integration testing
Acceptance test is performed by the client, not by the developer.
Alpha test:
Client uses the software at the developer’s environment.
Software used in a controlled setting, with the developer always ready to fix bugs.
Beta test:
Conducted at client’s environment (developer is not present)
Software gets a realistic workout in target environment
Majority of all bugs in software is typically found by the client after the system is in use,
not by the developers or testers. Therefore two kinds of additional tests:
Alpha test
Beta test: … One disadvantage: Potential customers might get discouraged

46. Testing has many activities
Establish the test objectives
Design the test cases
Write the test cases
Test the test cases
Execute the tests
Evaluate the test results
Change the system
Do regression testing

47. Test Team Test Team Professional Tester Analyst System Designer User
too familiar
Programmer
with code
Analyst
System
Designer
Test
User
Team
Configuration
Management
Specialist

48. The 4 Testing Steps 1. Select what has to be tested
Analysis: Completeness of requirements
Design: Cohesion
Implementation: Source code
2. Decide how the testing is done
Review or 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 (class, subsystem, system) being tested or about the attribute being measured
4. Create the test oracle
An oracle contains the predicted results for a set of test cases
The test oracle has to be written down before the actual testing takes place.

49. 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 and datastructures:
Force a division by zero
If the upper bound of an array is 10, then use 11 as index.
Rauslassen?

50. High Order Testing Validation testing System testing
Focus is on software requirements
System testing
Focus is on system integration
Alpha/Beta testing
Focus is on customer usage
Recovery testing
forces the software to fail in a variety of ways and verifies that recovery is properly performed
Security testing
verifies that protection mechanisms built into a system will, in fact, protect it from improper penetration
Stress testing
executes a system in a manner that demands resources in abnormal quantity, frequency, or volume
Performance Testing
test the run-time performance of software within the context of an integrated system

51. Regression Testing Conducted after a change
Regression test aims to verify whether new faults are introduced 51

52. Regression testing
Selective re-testing of a system or component to verify that modifications have not caused unintended effects
Can be conducted at each of the test levels: unit, integration, system
Modifications
Changed
Version X+1
Version X 52

53. Regression Testing
regression test is not a separate level of but may refer to the retesting of a unit, integration and system after modification, in order to ascertain that the change has not introduced new faults